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Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2018	May 02, 2018
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Entity Registrant Name	ASSEMBLY BIOSCIENCES, INC.
Entity Central Index Key	0001426800
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Trading Symbol	ASMB
Entity Common Stock, Shares Outstanding		20,550,718

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 66,926,630	$ 82,033,209
Marketable securities, at fair value	42,232,348	37,914,482
Accounts receivable from collaboration	2,263,556	2,273,421
Prepaid expenses and other current assets	1,803,066	897,400
Total current assets	113,225,600	123,118,512
Long-term assets
Marketable securities, at fair value	0	3,347,213
Property, plant and equipment, net	731,500	860,026
Security deposits	425,592	339,558
Intangible assets	29,000,000	29,000,000
Goodwill	12,638,136	12,638,136
Total long-term assets	42,795,228	46,184,933
Total assets	156,020,828	169,303,445
Current liabilities
Accounts payable	2,372,874	2,123,939
Accrued expenses	4,647,472	6,139,000
Deferred revenue - short-term	5,159,587	5,229,227
Total current liabilities	12,179,933	13,492,166
Long-term liabilities
Deferred tax liabilities	2,135,802	2,135,802
Deferred revenue - long-term	39,323,844	40,555,708
Total long-term liabilities	41,459,646	42,691,510
Total liabilities	53,639,579	56,183,676
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 0 shares issued and outstanding	0	0
Common stock, $0.001 par value; 50,000,000 shares authorized; 20,386,736 and 20,137,974 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	20,387	20,138
Additional paid-in capital	370,104,986	364,528,037
Accumulated other comprehensive loss	(459,350)	(392,391)
Accumulated deficit	(267,284,774)	(251,036,015)
Total stockholders' equity	102,381,249	113,119,769
Total liabilities and stockholders' equity	$ 156,020,828	$ 169,303,445

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	20,386,736	20,137,974
Common stock, shares outstanding	20,386,736	20,137,974

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Collaboration revenue	$ 3,565,060	$ 684,369
Operating expenses:
Research and development	14,541,174	10,573,739
General and administrative	5,696,035	4,040,459
Total operating expenses	20,237,209	14,614,198
Loss from operations	(16,672,149)	(13,929,829)
Other income (expenses)
Interest and other income	446,406	136,484
Realized loss from marketable securities	(23,016)	(137,248)
Total other income (expense)	423,390	(764)
Net loss	(16,248,759)	(13,930,593)
Other comprehensive (loss) income
Unrealized loss recognized in accumulated other comprehensive loss before reclassification	(89,975)	(61,156)
Reclassification adjustment of unrealized loss included in net loss	23,016	137,248
Comprehensive loss	$ (16,315,718)	$ (13,854,501)
Net loss per share, basic and diluted	$ (0.80)	$ (0.81)
Weighted average common shares outstanding, basic and diluted	20,231,804	17,268,280

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (16,248,759)	$ (13,930,593)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	168,086	31,916
Stock-based compensation	4,082,767	1,224,647
Realized loss from marketable securities	23,016	137,248
Changes in operating assets and liabilities:
Accounts receivable from collaboration	9,865	0
Prepaid expenses and other current assets	(905,666)	(687,497)
Accounts payable	248,935	(420,948)
Accrued expenses	(1,491,528)	(739,261)
Deferred revenue	(1,301,504)	49,315,631
Security deposits	(86,034)	13,766
Net cash (used in) provided by operating activities	(15,500,822)	34,944,909
Cash flows from investing activities
Purchases of fixed assets	(39,560)	0
Purchases of marketable securities	(13,031,628)	0
Redemptions of marketable securities	11,971,000	6,658,000
Net cash (used in) provided by investing activities	(1,100,188)	6,658,000
Cash flows from financing activities
Proceeds from the exercise of stock options	1,494,431	640,017
Net cash provided by financing activities	1,494,431	640,017
Net (decrease) increase in cash and cash equivalents	(15,106,579)	42,242,926
Cash and cash equivalents at the beginning of the period	82,033,209	28,575,085
Cash and cash equivalents at the end of the period	66,926,630	70,818,011
Supplemental disclosure of cash flow information:
Change in unrealized (loss) gain on marketable securities available-for-sale	$ (66,959)	$ 76,092

CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - 3 months ended Mar. 31, 2018 - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2017	$ 113,119,769	$ 20,138	$ 364,528,037	$ (392,391)	$ (251,036,015)
Balance (in Shares) at Dec. 31, 2017		20,137,974
Proceeds from the exercise of stock options	1,494,431	$ 249	1,494,182	0	0
Proceeds from the exercise of stock options (in shares)		248,762
Change in unrealized loss on marketable securities	(66,959)	$ 0	0	(66,959)	0
Stock-based compensation	4,082,767	0	4,082,767	0	0
Net loss	(16,248,759)	0	0	0	(16,248,759)
Balance at Mar. 31, 2018	$ 102,381,249	$ 20,387	$ 370,104,986	$ (459,350)	$ (267,284,774)
Balance (in Shares) at Mar. 31, 2018		20,386,736

Nature of Business

3 Months Ended

Mar. 31, 2018

Organization, Business and Basis Of Presentation [Abstract]

Nature of Business

Note 1 - Nature of Business

Overview

Assembly Biosciences, Inc., together with its subsidiaries (Assembly or the Company), is a clinical stage biotechnology company advancing two innovative platform programs: a new class of oral therapeutic candidates for the treatment of hepatitis B virus (HBV) infection and a novel class of oral synthetic live biotherapeutic candidates, which are designed to treat disorders associated with the microbiome.

Over 250 million people worldwide are chronically infected with HBV. The Company’s HBV-cure program is pursuing multiple drug candidates that inhibit the HBV lifecycle and block the generation of covalently closed circular DNA (cccDNA), with the aim of increasing the current low cure rates for patients with HBV. Assembly has discovered multiple novel core protein Allosteric Modifiers (CpAMs), which are small molecules that directly target and allosterically modify the HBV core (HBc) protein.

The Company’s Microbiome program consists of a fully integrated platform that includes a disease targeted strain identification and selection process, methods for strain isolation and growth under current Good Manufacturing Practices (cGMP) conditions, and a patented delivery system that we call GEMICEL®, which is designed to allow for targeted oral delivery of live biologic and conventional therapies to the lower gastrointestinal (GI) tract. Using its microbiome platform, the Company is developing product candidates for various disease indications, including ulcerative colitis, Crohn’s disease, irritable bowel syndrome, non-alcoholic steatohepatitis (NASH), immuno-oncology and Clostridium difficile infections (CDI), which the Company intends to develop either internally or in collaboration with partners.

On January 6, 2017, the Company entered into a Research, Development, Collaboration and License Agreement (the Collaboration Agreement) with Allergan Pharmaceuticals International Limited (Allergan) to develop and commercialize select microbiome gastrointestinal programs. Pursuant to the terms of the Collaboration Agreement, in connection with the closing of the transaction on February 10, 2017, Allergan paid the Company an upfront payment of $50 million. Additionally, the Company is eligible to receive up to approximately $630 million in payments related to seven development milestones and up to approximately $2.15 billion in payments related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications (see Note 7). Allergan and the Company have agreed to share development costs up to an aggregate of $75 million through proof-of-concept (POC) studies on a ⅔, ⅓ basis, respectively, and Allergan has agreed to assume all post-POC development costs. Additionally, the Company has an option to co-promote the licensed programs in the United States and China, subject to certain conditions set forth in the Collaboration Agreement.

Liquidity

The Company has not derived any revenue from product sales to date and currently has no approved products. Once a product has been developed, it will need to be approved for sale by the U.S. Food and Drug Administration (FDA) or an applicable foreign regulatory agency. Since inception, the Company’s operations have been financed primarily through the sale of equity securities, the proceeds from the exercise of warrants and stock options, the issuance of debt and an up-front payment related to the Collaboration Agreement. The Company has incurred losses from operations and negative cash flows from operating activities since inception and expects to continue to incur substantial losses for the next several years as it continues its product development efforts. Management believes the Company currently has sufficient funds to meet its operating requirements for at least the next twelve months. If the Company cannot generate significant cash from its operations, it intends to obtain any additional funding it requires through strategic relationships, public or private equity or debt financings, grants or other arrangements. The Company cannot assure such funding will be available on reasonable terms, if at all.

If the Company is unable to generate enough revenue from the Collaboration Agreement when needed or to secure additional sources of funding and receive related full and timely collections of amounts due, it may be necessary to significantly reduce the current rate of spending through reductions in staff and delaying, scaling back, or stopping certain research and development programs, including more costly clinical trials.

Summary of Significant Accounting Policies and Recent Accounting Pronouncements

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies and Recent Accounting Pronouncements

Note 2 - Summary of Significant Accounting Policies and Recent Accounting Pronouncements

Basis of Presentation

The accompanying condensed consolidated interim financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

The accompanying condensed consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and pursuant to the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the U.S. Securities and Exchange Commission (SEC) and on the same basis as the Company prepares its annual audited consolidated financial statements. The condensed consolidated balance sheet at March 31, 2018, condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2018 and 2017, condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017, and condensed consolidated statement of changes in stockholders’ equity for the three months ended March 31, 2018 are unaudited, but include all adjustments, consisting only of normal recurring adjustments, that the Company considers necessary for a fair presentation of the financial position, operating results and cash flows for the periods presented. The results for the three months ended March 31, 2018 are not necessarily indicative of results to be expected for the year ending December 31, 2018 or for any future interim period. The consolidated balance sheet at December 31, 2017 has been derived from audited financial statements; however, it does not include all of the information and notes required by U.S. GAAP for complete financial statements. The accompanying condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2017 and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 filed with the SEC on March 8, 2018 (the 2017 Annual Report).

Use of Estimates

The preparation of the condensed consolidated financial statements in conformity with the U.S. GAAP requires management to make estimates and assumptions that may affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting period. Actual results could differ from those estimates.

Significant estimates inherent in the preparation of the accompanying condensed consolidated financial statements include recoverability and useful lives (indefinite or finite) of intangible assets, assessment of impairment of goodwill, provisions for income taxes, timing of revenue recognition and allocation of the transaction price to performance obligations, and the fair value of stock options and warrants granted to employees, consultants, directors, investors, licensors, placement agents and underwriters.

The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible that these external factors could have an effect on the Company’s estimates and could cause actual results to differ from those estimates and assumptions.

Significant Accounting Policies

There have been no material changes in the Company’s significant accounting policies to those previously disclosed in the 2017 Annual Report other than the adoption of the Financial Accounting Standards Board (FASB) Accounting Standard Updates (ASU) 606, Revenue from Contracts with Customers (see Note 7).

Loss per Share of Common Stock

Basic net loss per share of common stock excludes dilution and is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity unless inclusion of such shares would be anti-dilutive. Since the Company has only incurred losses, basic and diluted net loss per share is the same. Securities that could potentially result in diluted loss per share in the future that were not included in the computation of diluted loss per share at March 31, 2018 and 2017 are as follows:

	March 31,
	2018		2017
Warrants to purchase common stock		15,296		16,909
Options to purchase common stock		4,826,361		4,816,126
Restricted stock units		251,559		-
Total		5,093,216		4,833,035

Revenue Recognition

The Company recognizes revenue under ASC 606, Revenue from Contracts with Customers. The core principle of the new revenue standard is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The following five steps are applied to achieve that core principle:

⋅	Step 1: Identify the contract with the customer

⋅	Step 2: Identify the performance obligations in the contract

⋅	Step 3: Determine the transaction price

⋅	Step 4: Allocate the transaction price to the performance obligations in the contract

⋅	Step 5: Recognize revenue when the company satisfies a performance obligation

In order to identify the performance obligations in a contract with a customer, a company must assess the promised goods or services in the contract and identify each promised good or service that is distinct. A performance obligation meets ASC 606’s definition of a “distinct” good or service (or bundle of goods or services) if both of the following criteria are met:

the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (i.e., the good or service is capable of being distinct); and

the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (i.e., the promise to transfer the good or service is distinct within the context of the contract).

If a good or service is not distinct, the good or service is combined with other promised goods or services until a bundle of goods or services is identified that is distinct.

The transaction price is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties (for example, some sales taxes). The consideration promised in a contract with a customer may include fixed amounts, variable amounts or both. When determining the transaction price, an entity must consider the effects of all of the following:

·	variable consideration;

·	constraining estimates of variable consideration;

·	existence of a significant financing component in the contract;

·	noncash consideration; and

·	consideration payable to a customer.

Variable consideration is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved.

The transaction price is allocated to each performance obligation on a relative standalone selling price basis.

The transaction price allocated to each performance obligation is recognized when that performance obligation is satisfied, at a point in time or over time as appropriate.

Revenue for a sales-based or usage-based royalty promised in exchange for a license of intellectual property is recognized only when (or as) the later of the following events occurs:

·	the subsequent sale or usage occurs; or

·	the performance obligation to which some or all of the sales-based or usage-based royalty has been allocated has been satisfied (or partially satisfied).

Adoption of Recent Accounting Pronouncements

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), as modified by ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, and ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients. The revenue recognition principle in ASU 2014-09 is that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, new and enhanced disclosures will be required. Companies may adopt the new standard either using the full retrospective approach, a modified retrospective approach with practical expedients, or a cumulative effect upon adoption approach. The Company adopted the new standard on January 1, 2018 using the modified retrospective approach. The Collaboration Agreement is the Company’s only revenue contract, and adoption of ASU 2014-09 did not have any impact on the Company’s accounting for this agreement in the accompanying condensed consolidated financial statements.

In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 requires equity investments to be measured at fair value with changes in fair value recognized in net income; simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial assets on the balance sheet or the accompanying notes to the financial statements and clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. ASU 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. On January 1, 2018, the Company implemented ASU 2016-01 without any impact on the Company’s condensed consolidated financial statements and related disclosures.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments, which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. On January 1, 2018, the Company implemented ASU 2016-15 without any material impact on the Company’s condensed consolidated statement of cash flows and related disclosures.

In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 provides clarity and reduces both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, to a change to the terms or conditions of a share-based payment award. The amendments in ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. On January 1, 2018, the Company implemented ASU 2017-09 without any material impact on the Company’s condensed consolidated financial statements and related disclosures.

Recent Accounting Pronouncements

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) which supersedes FASB Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. In January 2018, the FASB issued ASU 2018-01, Leases (Topic 842) Land Easement Practical Expedient for Transition to Topic 842, which amends ASU 2016-02 to provide entities an optional transition practical expedient to not evaluate under Topic 842 existing or expired land easements that were not previously accounted for as leases under the current leases guidance in Topic 842. An entity that elects this practical expedient should evaluate new or modified land easements under Topic 842 beginning at the date that the entity adopts Topic 842. The standard will be effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is currently evaluating the effect that the updated standard will have on its condensed consolidated financial statements and related disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments. ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The new standard will be effective on January 1, 2020. Early adoption will be available on January 1, 2019. The Company is currently evaluating the effect that the updated standard will have on its condensed consolidated financial statements and related disclosures.

In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income, (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate income tax rate under the Tax Cuts and Jobs Act. The amount of the reclassification would be the difference between the historical corporate income tax rate and the newly enacted 21% corporate income tax rate. The new standard is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2018 with early adoption in any interim period permitted. The Company is currently evaluating the effect that the updated standard will have on its condensed consolidated financial statements and related disclosures.

Marketable Securities

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Note 3 - Marketable Securities

Marketable securities consist of the following as of March 31, 2018 and December 31, 2017:

	March 31, 2018
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Short-term available-for-sale securities
Corporate bonds	$	39,411,091	$	3,335	$	(260,507)	$	39,153,919
Commercial paper		2,078,212		1,657		-		2,079,869
U.S. Treasury Securities		998,672		-		(112)		998,560
Total short-term available-for-sale securities	$	42,487,975	$	4,992	$	(260,619)	$	42,232,348
Total	$	42,487,975	$	4,992	$	(260,619)	$	42,232,348

	December 31, 2017
	Amortized Cost		Gross Unrealized Gain ⁽¹⁾		Gross Unrealized Loss ⁽¹⁾		Fair Value
Short-term available-for-sale securities
Corporate bonds	$	38,092,585	$	5,635	$	(183,738)	$	37,914,482

Long-term available-for-sale securities
Corporate bonds		3,357,778		-		(10,565)		3,347,213
Total	$	41,450,363	$	5,635	$	(194,303)	$	41,261,695

⁽¹⁾

Gross unrealized gain (loss) is pre-tax.

The contractual term to maturity of short-term marketable securities held by the Company as of March 31, 2018 is less than one year.

The fair value of marketable securities was classified into fair value measurement categories as of March 31, 2018 and December 31, 2017 as follows:

	March 31,		December 31,
	2018		2017
Quoted prices in active markets for identical assets (Level 1)	$	-	$	-
Quoted prices for similar assets observable in the marketplace (Level 2)		42,232,348		41,261,695
Significant unobservable inputs (Level 3)		-		-
Total	$	42,232,348	$	41,261,695

The fair values of marketable securities are determined using quoted market prices from daily exchange traded markets based on the closing prices as of March 31, 2018 and December 31, 2017.

There were no transfers of marketable securities between Levels 1, 2 or 3 for the three months ended March 31, 2018 and 2017.

The following table shows the Company’s investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2018.

	Less than 12 Months				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Corporate bonds	$	35,407,491	$	(260,507)	$	35,407,491	$	(260,507)
U.S. Treasury Securities		998,560		(112)		998,560		(112)
Total	$	36,406,051	$	(260,619)	$	36,406,051	$	(260,619)

The Company has determined that the unrealized losses are deemed to be temporary as of March 31, 2018. The Company believes that the unrealized losses generally are caused by increases in the risk premiums required by market participants rather than an adverse change in cash flows or a fundamental weakness in the credit quality of the issuer or underlying assets. Because the Company has the ability and intent to hold these investments until a recovery of fair value, which may be maturity, it does not consider the investment in corporate bonds to be other-than-temporarily impaired at March 31, 2018.

Property, Plant and Equipment, Net

3 Months Ended

Mar. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, Net

Note 4 - Property, Plant and Equipment, Net

Property, plant and equipment, consists of the following:

	Useful life	March 31,		December 31,
	(Years)	2018		2017
Computer hardware and software	3	$	114,683	$	104,968
Lab equipment	3 to 5		369,827		369,827
Office equipment	7		55,199		25,354
Leasehold improvement	1 to 3.25		773,700		773,700
Total property, plant and equipment			1,313,409		1,273,849
Less: Accumulated depreciation and amortization			(581,909)		(413,823)
Property, plant and equipment, net		$	731,500	$	860,026

Depreciation expense for the three months ended March 31, 2018 and 2017 was $168,086 and $31,916, respectively, and was recorded in both research and development expense and general and administrative expense in the condensed consolidated statements of operations.

Accrued Expenses

3 Months Ended

Mar. 31, 2018

Payables and Accruals [Abstract]

Accrued Expenses

Note 5 - Accrued Expenses

Accrued expenses consist of the following:

	March 31,		December 31,
	2018		2017
Accrued expenses:
Salaries, bonuses and employee benefits	$	1,307,440	$	4,518,128
Research and development expenses		2,310,505		674,686
General and administrative expenses		1,029,527		946,186
Total accrued expenses	$	4,647,472	$	6,139,000

Stockholders’ Equity

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Stockholders' Equity

Note 6 - Stockholders’ Equity

Common Stock

For the three months ended March 31, 2018, the Company issued an aggregate of 248,762 shares of common stock, and received gross proceeds of approximately $1.5 million from the exercise of options.

Preferred Stock

On January 24, 2018, the Board authorized the filing of a Certificate of Elimination with the Secretary of State of the State of Delaware to remove the Certificate of Designation of Series A Non-Voting Convertible Preferred Stock (the Series A Preferred Stock) from the Company’s Third Amended and Restated Certificate of Incorporation, as amended, because no shares of the Series A Preferred Stock were outstanding and no shares were available to be issued.

Options

In July 2010, the Company’s stockholders approved the 2010 Equity Incentive Plan (the 2010 Plan) and on May 19, 2011, the Company’s stockholders approved an amendment to the 2010 Plan increasing the authorized shares thereunder to 793,440, on a post-Split Effective Time basis. As of March 31, 2018, there were outstanding options to purchase an aggregate of 585,584 shares of common stock. Effective on June 2, 2016, the 2010 Plan was frozen and no further grants will be made under the 2010 Plan. Shares that are forfeited under the 2010 Plan on or after June 2, 2016 will become available for issuance under the Amended and Restated 2014 Plan (as defined below).

In July 2014, the Company’s stockholders approved the 2014 Stock Incentive Plan (the 2014 Plan). On June 2, 2016, at the 2016 Annual Meeting of Stockholders, the Company’s stockholders approved the amendment and restatement of the Company’s 2014 Plan (the Amended and Restated 2014 Plan). Pursuant to the terms of the Amended and Restated 2014 Plan, the maximum number of shares reserved for issuance thereunder is 4,160,000. As of March 31, 2018, there were outstanding options to purchase an aggregate of 3,336,988 shares of common stock and 251,559 shares of common stock underlying outstanding restricted stock units (RSUs), and 181,078 shares available for grant under the Amended and Restated 2014 Plan.

On April 3, 2017, the Company’s Board of Directors adopted the Assembly Biosciences, Inc. 2017 Inducement Award Plan (the Inducement Plan) pursuant to which the Company reserved 800,000 shares of common stock for issuance under the Inducement Plan. The only persons eligible to receive grants of awards under the Inducement Plan are individuals who satisfy the standards for inducement grants under Nasdaq Marketplace Rule 5635(c)(4) and the related guidance under Nasdaq IM-5635-1. An “Award” is any right to receive Assembly common stock pursuant to the Inducement Plan, consisting of nonstatutory stock options, stock appreciation rights, dividend equivalent rights, restricted stock awards, restricted stock unit awards, or any other stock award. As of March 31, 2018, there were outstanding options to purchase an aggregate of 437,550 shares of common stock and 362,450 shares available for grant under the Inducement Plan.

On March 8, 2018, the Company appointed Graham Cooper as the Company’s Chief Financial Officer and Chief Operating Officer. Mr. Cooper will also serve as the Company’s principal financial officer and principal accounting officer. In connection with his appointment, Mr. Cooper also was granted a non-qualified stock option to purchase 220,000 shares of the Company’s common stock. The option vests over three years as follows: one-third will vest on the first anniversary of the date of grant, March 8, 2019; and the remaining two-thirds will vest in 24 equal monthly installments, with the option becoming fully vested on March 8, 2021. The option is subject to Mr. Cooper’s continued service with Assembly through the applicable vesting dates and to acceleration upon the occurrence of certain events as set forth in the option agreement and his employment agreement.

A summary of the Company’s option activity and related information for the three-month period ended March 31, 2018 is as follows:

	Number of Shares		Weighted Average Exercise Price Per Share		Total Intrinsic Value
Outstanding as of December 31, 2017		4,551,819	$	9.66	$	162,002,439
Granted		534,804		53.06		-
Exercised		(248,762)		6.01		-
Forfeited		(11,500)		16.65		-
Outstanding as of March 31, 2018		4,826,361	$	14.64	$	168,652,906
Options vested and exercisable		3,150,559	$	7.70	$	130,548,017

The fair value of the options granted for the three months ended March 31, 2018 and 2017, were based on the following assumptions:

	Three Months Ended March 31,
	2018	2017
Exercise price	$45.80 - $57.53	$12.81 - $25.34
Expected stock price volatility	77.0% - 86.1%	85.4% - 87.0%
Risk-free rate of interest	2.57% - 2.79%	2.19% - 2.23%
Term (years)	5.5 - 7.0	5.5 - 7.0

Estimated future stock-based compensation expense relating to unvested stock options is as follows:

	Future Stock Option Compensation Expenses
Nine Months Ending December 31, 2018	$	12,899,608
Year Ending December 31, 2019		8,690,702
Year Ending December 31, 2020		3,254,762
Year Ending December 31, 2021		676,700
Year Ending December 31, 2022		25,487
Total	$	25,547,259

The weighted average remaining contractual term of exercisable options is approximately 6.7 years at March 31, 2018.

Warrants

There was no warrant activity during the three months ended March 31, 2018. The weighted average remaining contractual life of outstanding warrants to purchase 15,296 shares of common stock at March 31, 2018 is approximately 2.4 years.

Restricted Stock Units

On December 8, 2017, the Company issued 120,000 RSUs to its Chief Scientific Officer, Richard Colonno. The RSUs will vest upon the occurrence of specified performance milestones; provided that none of these RSUs will vest prior to August 1, 2018. On March 29, 2018, the Company issued 131,559 RSUs to employees as annual performance awards, which RSUs will vest over four years assuming continuous service by the applicable employees through the vesting dates.

A summary of the Company's restricted stock units and related information is as follows:

	Number of units		Weighted average grant price
Unvested as of December 31, 2017		120,000	$	44.28
Granted		131,559		49.14
Unvested as of March 31, 2018		251,559	$	46.82

As of March 31, 2018, the Company had unrecognized stock-based compensation expense related to all unvested restricted stock units of $10.1 million. The weighted average remaining contractual term of unvested RSUs is approximately 9.9 years at March 31, 2018.

Stock-based compensation expense for the three months ended March 31, 2018 and 2017 is as follows:

	Three Months Ended March 31,
	2018		2017
Research and development	$	2,524,108	$	951,926
General and administrative		1,558,659		272,721
Total stock-based compensation expense	$	4,082,767	$	1,224,647

Collaboration Agreement

3 Months Ended

Mar. 31, 2018

Organization, Business and Basis Of Presentation [Abstract]

Collaboration Agreement

Note 7 – Collaboration Agreement

On January 6, 2017, the Company entered into the Collaboration Agreement with Allergan to develop and commercialize select microbiome gastrointestinal programs. Pursuant to the Collaboration Agreement, the Company granted Allergan an exclusive worldwide license to certain of its intellectual property, including its intellectual property arising under the Collaboration Agreement, to develop and commercialize licensed compounds for ulcerative colitis (UC), Crohn’s disease, and irritable bowel syndrome (IBS). Allergan and the Company will collaborate on research and development activities with respect to the licensed compounds in accordance with a mutually agreed upon research and development plan.

In connection with the closing of the transaction on February 10, 2017, Allergan paid the Company an upfront payment of $50 million. Additionally, the Company is eligible to receive variable consideration in the form of cost-sharing reimbursements, up to approximately $630 million in related to seven development milestones and up to approximately $2.15 billion in related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications. There is significant uncertainty as to whether the stated milestones will be achieved, and the Company has not included the associated variable consideration in the transaction price as it is not probable that a significant reversal in the amount of cumulative revenue recognized would not occur.

In addition, the Company is eligible to receive tiered royalties at rates ranging from the mid-single digits to the mid-teens based on net sales. Allergan and the Company have agreed to share development costs up to an aggregate of $75 million through proof-of-concept (POC) studies on a ⅔, ⅓ basis, respectively, and Allergan has agreed to assume all post-POC development costs. In the event any pre-POC development costs exceed $75 million in the aggregate, the Company may elect either (a) to fund ⅓ of such costs in excess of $75 million or (b) to allow Allergan to deduct from future development milestone payments ⅓ of the development costs funded by Allergan in excess of $75 million plus a premium of 25%. The Company has an option to co-promote the licensed programs in the U.S. and China, subject to certain conditions set forth in the Collaboration Agreement. Allergan may terminate the Collaboration Agreement for convenience at any time upon either 90 days’ (prior to the initiation of the first POC trial of a licensed product) or 120 days’ (after the initiation of the first POC trial of a licensed product), as applicable, advance written notice to the Company. The Collaboration Agreement also contains customary provisions for termination by either party, including in the event of breach of the Collaboration Agreement, subject to cure.

The Company determined that it has four performance obligations under the Collaboration Agreement associated with the transfer of the license and the performance of the research and development services combined for each of the four indications; the license is not distinct because Allergan cannot obtain value from the license without the research and development services that the Company is uniquely able to perform. The deferred revenue associated with the $50 million upfront payment will be recorded proportionally over a ten-year service period as the research and development services are expected to be performed. As such, the Company recognized the upfront payment received of $50.0 million as approximately $5.0 million in short-term deferred revenue and $45.0 million in long-term deferred revenue as of the closing date. Given the early stage of development, the Company has determined the relative selling price for each of the four indications to be $12.5 million. For the three months ended March 31, 2018 and 2017, the Company recorded approximately $1.3 million and approximately $0.7 million, respectively, in revenue related to the amortization of deferred revenue. Short-term and long-term deferred revenue contract liabilities related to the Collaboration Agreement were approximately $5.2 million and approximately $39.3 million at March 31, 2018 and approximately $5.2 million and approximately $40.6 million at December 31, 2017.

Expense reimbursements will be recognized as collaboration revenue when the related expenses are incurred. The reimbursable expenses incurred in connection with the Collaboration Agreement during the three months ended March 31, 2018 and 2017 were approximately $2.3 million and nil, respectively, and recorded in collaboration revenue on the condensed consolidated statement of operations. In the condensed consolidated balance sheets, contract balances of approximately $2.3 million and approximately $2.3 million were recorded as accounts receivable from collaboration as of March 31, 2018 and December 31, 2017, respectively. As of January 1, 2018 and March 31, 2018, the Company had a contract liability balance of $0.2 million related to expense reimbursement performance obligations that were not satisfied.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 8 - Commitments and Contingencies

Real Property Leases and Equipment Leases

The Company leases office space for corporate functions in Carmel, Indiana under a lease agreement that expires in August 2023. The leased location in Carmel, Indiana supports both the HBV-cure and Microbiome programs. The Company leases office and laboratory space in San Francisco, California under a sublease that expires in December 2018 unless the Company requests a six-month extension. The leased location in San Francisco, California supports both the HBV-cure and Microbiome programs. The Company also conducts research activities for the Microbiome program at office and laboratory space in Groton, Connecticut under a lease that expires in March 2019.

The total leasing expenses for the three months ended March 31, 2018 and 2017 were approximately $0.4 million and $0.3 million, respectively.

Equipment Lease

Pursuant to a Master Lease agreement dated November 25, 2014, the Company leases certain equipment. The equipment lease expense for the three months ended March 31, 2018 and 2017 amounted to approximately $304,000 and $182,000, respectively. These equipment leases began to expire in 2017, with the final lease expiring in 2021. The sum of all future payments through termination is approximately $2.6 million.

Litigation

The Company is not a party to any material legal proceedings. From time to time, the Company may be subject to various legal proceedings and claims that arise in the ordinary course of its business activities.

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of presentation

Basis of Presentation

Use of Estimates

Use of Estimates

Significant Accounting Policies

Significant Accounting Policies

Loss per Share of Common Stock

Loss per Share of Common Stock

	March 31,
	2018		2017
Warrants to purchase common stock		15,296		16,909
Options to purchase common stock		4,826,361		4,816,126
Restricted stock units		251,559		-
Total		5,093,216		4,833,035

Revenue Recognition

Revenue Recognition

⋅	Step 1: Identify the contract with the customer

⋅	Step 2: Identify the performance obligations in the contract

⋅	Step 3: Determine the transaction price

⋅	Step 4: Allocate the transaction price to the performance obligations in the contract

⋅	Step 5: Recognize revenue when the company satisfies a performance obligation

If a good or service is not distinct, the good or service is combined with other promised goods or services until a bundle of goods or services is identified that is distinct.

·	variable consideration;

·	constraining estimates of variable consideration;

·	existence of a significant financing component in the contract;

·	noncash consideration; and

·	consideration payable to a customer.

The transaction price is allocated to each performance obligation on a relative standalone selling price basis.

The transaction price allocated to each performance obligation is recognized when that performance obligation is satisfied, at a point in time or over time as appropriate.

Revenue for a sales-based or usage-based royalty promised in exchange for a license of intellectual property is recognized only when (or as) the later of the following events occurs:

·	the subsequent sale or usage occurs; or

·	the performance obligation to which some or all of the sales-based or usage-based royalty has been allocated has been satisfied (or partially satisfied).

Recent Accounting Pronouncements

Adoption of Recent Accounting Pronouncements

Recent Accounting Pronouncements

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

Securities that could potentially result in diluted loss per share in the future that were not included in the computation of diluted loss per share at March 31, 2018 and 2017 are as follows:

	March 31,
	2018		2017
Warrants to purchase common stock		15,296		16,909
Options to purchase common stock		4,826,361		4,816,126
Restricted stock units		251,559		-
Total		5,093,216		4,833,035

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation

Marketable securities consist of the following as of March 31, 2018 and December 31, 2017:

	March 31, 2018
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Short-term available-for-sale securities
Corporate bonds	$	39,411,091	$	3,335	$	(260,507)	$	39,153,919
Commercial paper		2,078,212		1,657		-		2,079,869
U.S. Treasury Securities		998,672		-		(112)		998,560
Total short-term available-for-sale securities	$	42,487,975	$	4,992	$	(260,619)	$	42,232,348
Total	$	42,487,975	$	4,992	$	(260,619)	$	42,232,348

	December 31, 2017
	Amortized Cost		Gross Unrealized Gain ⁽¹⁾		Gross Unrealized Loss ⁽¹⁾		Fair Value
Short-term available-for-sale securities
Corporate bonds	$	38,092,585	$	5,635	$	(183,738)	$	37,914,482

Long-term available-for-sale securities
Corporate bonds		3,357,778		-		(10,565)		3,347,213
Total	$	41,450,363	$	5,635	$	(194,303)	$	41,261,695

⁽¹⁾

Gross unrealized gain (loss) is pre-tax

Schedule Of Available For Sale Securities Fair Value Measurement Categories

The fair value of marketable securities was classified into fair value measurement categories as of March 31, 2018 and December 31, 2017 as follows:

	March 31,		December 31,
	2018		2017
Quoted prices in active markets for identical assets (Level 1)	$	-	$	-
Quoted prices for similar assets observable in the marketplace (Level 2)		42,232,348		41,261,695
Significant unobservable inputs (Level 3)		-		-
Total	$	42,232,348	$	41,261,695

Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value

	Less than 12 Months				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Corporate bonds	$	35,407,491	$	(260,507)	$	35,407,491	$	(260,507)
U.S. Treasury Securities		998,560		(112)		998,560		(112)
Total	$	36,406,051	$	(260,619)	$	36,406,051	$	(260,619)

Property, Plant and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, plant and equipment, consists of the following:

	Useful life	March 31,		December 31,
	(Years)	2018		2017
Computer hardware and software	3	$	114,683	$	104,968
Lab equipment	3 to 5		369,827		369,827
Office equipment	7		55,199		25,354
Leasehold improvement	1 to 3.25		773,700		773,700
Total property, plant and equipment			1,313,409		1,273,849
Less: Accumulated depreciation and amortization			(581,909)		(413,823)
Property, plant and equipment, net		$	731,500	$	860,026

Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2018

Payables and Accruals [Abstract]

Schedule Accrued Expenses

Accrued expenses consist of the following:

	March 31,		December 31,
	2018		2017
Accrued expenses:
Salaries, bonuses and employee benefits	$	1,307,440	$	4,518,128
Research and development expenses		2,310,505		674,686
General and administrative expenses		1,029,527		946,186
Total accrued expenses	$	4,647,472	$	6,139,000

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' Transactions [Abstract]

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award

A summary of the Company’s option activity and related information for the three-month period ended March 31, 2018 is as follows:

	Number of Shares		Weighted Average Exercise Price Per Share		Total Intrinsic Value
Outstanding as of December 31, 2017		4,551,819	$	9.66	$	162,002,439
Granted		534,804		53.06		-
Exercised		(248,762)		6.01		-
Forfeited		(11,500)		16.65		-
Outstanding as of March 31, 2018		4,826,361	$	14.64	$	168,652,906
Options vested and exercisable		3,150,559	$	7.70	$	130,548,017

Assumptions for Weighted Average Fair Value of Options Granted

The fair value of the options granted for the three months ended March 31, 2018 and 2017, were based on the following assumptions:

	Three Months Ended March 31,
	2018	2017
Exercise price	$45.80 - $57.53	$12.81 - $25.34
Expected stock price volatility	77.0% - 86.1%	85.4% - 87.0%
Risk-free rate of interest	2.57% - 2.79%	2.19% - 2.23%
Term (years)	5.5 - 7.0	5.5 - 7.0

Estimated Future Stock Based Expenses Relating to Unvested Stock Options

Estimated future stock-based compensation expense relating to unvested stock options is as follows:

	Future Stock Option Compensation Expenses
Nine Months Ending December 31, 2018	$	12,899,608
Year Ending December 31, 2019		8,690,702
Year Ending December 31, 2020		3,254,762
Year Ending December 31, 2021		676,700
Year Ending December 31, 2022		25,487
Total	$	25,547,259

Schedule of Restricted Stock Number of units

A summary of the Company's restricted stock units and related information is as follows:

	Number of units		Weighted average grant price
Unvested as of December 31, 2017		120,000	$	44.28
Granted		131,559		49.14
Unvested as of March 31, 2018		251,559	$	46.82

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

Stock-based compensation expense for the three months ended March 31, 2018 and 2017 is as follows:

	Three Months Ended March 31,
	2018		2017
Research and development	$	2,524,108	$	951,926
General and administrative		1,558,659		272,721
Total stock-based compensation expense	$	4,082,767	$	1,224,647

Nature of Business - Additional Information (Details) $ in Millions	Feb. 10, 2017 USD ($)
Overview [Line Items]
Licenses Revenue	$ 50
Development Milestone Payments	630
Commercial Milestone Payments	$ 2,150
Revenue Recognition, Milestone Method, Description	the Company is eligible to receive variable consideration in the form of cost-sharing reimbursements, up to approximately $630 million in related to seven development milestones and up to approximately $2.15 billion in related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications
Allergan Pharmaceuticals International Limited [Member]
Overview [Line Items]
Agreed To Share Maximum Amount Development Cost	$ 75
Revenue Recognition, Milestone Method, Description	the Company is eligible to receive up to approximately $630 million in payments related to seven development milestones and up to approximately $2.15 billion in payments related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,093,216	4,833,035
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	251,559	0
Warrants To Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	15,296	16,909
Options To Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,826,361	4,816,126

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018
Scenario, Plan [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%

Marketable Securities (Details) - USD ($)

Mar. 31, 2018

Dec. 31, 2017

Schedule of Available-for-sale Securities [Line Items]

Amortized Cost

$ 42,487,975

$ 41,450,363

Gross Unrealized Gain

4,992

5,635

^[1]

Gross Unrealized Loss

(260,619)

(194,303)

^[1]

Fair Value

42,232,348

41,261,695

Short-term Investments [Member] | Corporate Bond Securities [Member]

Schedule of Available-for-sale Securities [Line Items]

Amortized Cost

39,411,091

38,092,585

Gross Unrealized Gain

3,335

5,635

^[1]

Gross Unrealized Loss

(260,507)

(183,738)

^[1]

Fair Value

39,153,919

37,914,482

Short-term Investments [Member] | Commercial Paper [Member]

Schedule of Available-for-sale Securities [Line Items]

Amortized Cost

2,078,212

Gross Unrealized Gain

1,657

Gross Unrealized Loss

Fair Value

2,079,869

Short-term Investments [Member] | U.S. Treasury Securities [Member]

Schedule of Available-for-sale Securities [Line Items]

Amortized Cost

998,672

Gross Unrealized Gain

Gross Unrealized Loss

(112)

Fair Value

$ 998,560

Long-term Investments [Member] | Corporate Bond Securities [Member]

Schedule of Available-for-sale Securities [Line Items]

Amortized Cost

3,357,778

Gross Unrealized Gain

^[1]

Gross Unrealized Loss

^[1]

(10,565)

Fair Value

$ 3,347,213

[1]	Gross unrealized gain (loss) is pre-tax.

Marketable Securities (Details 1) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 42,232,348	$ 41,261,695
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	42,232,348	41,261,695
Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 0	$ 0

Marketable Securities (Details 2)	Mar. 31, 2018 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 36,406,051
Unrealized Losses, Less than 12 Months	(260,619)
Fair Value, Total	36,406,051
Unrealized Losses, Total	(260,619)
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	35,407,491
Unrealized Losses, Less than 12 Months	(260,507)
Fair Value, Total	35,407,491
Unrealized Losses, Total	(260,507)
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	998,560
Unrealized Losses, Less than 12 Months	(112)
Fair Value, Total	998,560
Unrealized Losses, Total	$ (112)

Marketable Securities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018
Short-term Investments [Member]
Available For Sale Securities Maturity Term	less than one year

Property, Plant and Equipment, Net (Details) - USD ($)	3 Months Ended
Property, Plant and Equipment, Net (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 1,313,409	$ 1,273,849
Less: Accumulated depreciation and amortization	(581,909)	(413,823)
Property, plant and equipment, net	731,500	860,026
Computer hardware and software [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 114,683	104,968
Property, Plant and Equipment, Useful Life	3 years
Lab equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 369,827	369,827
Lab equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Lab equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Office equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 55,199	25,354
Property, Plant and Equipment, Useful Life	7 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 773,700	$ 773,700
Leasehold improvements [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	1 year
Leasehold improvements [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years 3 months

Property, Plant and Equipment, Net - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation	$ 168,086	$ 31,916

Accrued Expenses (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Accrued expenses:
Salaries, bonuses and employee benefits	$ 1,307,440	$ 4,518,128
Research and development expenses	2,310,505	674,686
General and administrative expenses	1,029,527	946,186
Total accrued expenses	$ 4,647,472	$ 6,139,000

Stockholders' Equity (Details) - Stock Option [Member]	3 Months Ended
Stockholders' Equity (Details) - Stock Option [Member]	Mar. 31, 2018 USD ($) $ / shares shares
Number of Shares
Option, Outstanding at beginning of period \| shares	4,551,819
Option, Granted \| shares	534,804
Option, Exercised \| shares	(248,762)
Option, Forfeited \| shares	(11,500)
Option, Outstanding at end of period \| shares	4,826,361
Options vested and exercisable \| shares	3,150,559
Weighted Average Exercise Price Per Share
Option, Outstanding at beginning of period \| $ / shares	$ 9.66
Option, Granted \| $ / shares	53.06
Option, Exercised \| $ / shares	6.01
Option, Forfeited \| $ / shares	16.65
Option, Outstanding at end of period \| $ / shares	14.64
Options vested and exercisable \| $ / shares	$ 7.7
Total Intrinsic Value
Option, Outstanding at beginning of period \| $	$ 162,002,439
Option, Granted \| $	0
Option, Exercised \| $	0
Option, Forfeited \| $	0
Option, Outstanding at end of period \| $	168,652,906
Options vested and exercisable \| $	$ 130,548,017

Stockholders' Equity (Details 1) - $ / shares	3 Months Ended
Stockholders' Equity (Details 1) - $ / shares	Mar. 31, 2018	Mar. 31, 2017
Maximum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Exercise price	$ 57.53	$ 25.34
Expected stock price volatility	86.10%	87.00%
Risk-free rate of interest	2.79%	2.23%
Term (years)	7 years	7 years
Minimum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Exercise price	$ 45.80	$ 12.81
Expected stock price volatility	77.00%	85.40%
Risk-free rate of interest	2.57%	2.19%
Term (years)	5 years 6 months	5 years 6 months

Stockholders' Equity (Details 2)	Mar. 31, 2018 USD ($)
Stockholders Equity Note [Line Items]
Nine Months Ending December 31, 2018	$ 12,899,608
Year Ending December 31, 2019	8,690,702
Year Ending December 31, 2020	3,254,762
Year Ending December 31, 2021	676,700
Year Ending December 31, 2022	25,487
Total	$ 25,547,259

Stockholders' Equity (Details 3) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Number of units
Beginning of period \| shares	120,000
Number of units, Granted \| shares	131,559
Ending of period \| shares	251,559
Weighted average grant price
Beginning of period \| $ / shares	$ 44.28
Weighted average grant price, Granted \| $ / shares	49.14
Ending of period \| $ / shares	$ 46.82

Stockholders' Equity (Details 4) - USD ($)	3 Months Ended
Stockholders' Equity (Details 4) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	$ 4,082,767	$ 1,224,647
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	2,524,108	951,926
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated Share-based Compensation Expense	$ 1,558,659	$ 272,721

Stockholders' Equity - Additional Information (Details) - USD ($) $ in Millions		1 Months Ended		3 Months Ended
	Dec. 08, 2017	Mar. 29, 2018	May 19, 2011	Mar. 31, 2018	Dec. 31, 2017	Apr. 03, 2017	Jun. 02, 2016
Stockholders Equity Note [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance						800,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term				6 years 8 months 12 days
Proceeds from Stock Options Exercised				$ 1.5
Share Based Compensation Arrangement By Share Based Payment Award Options Non Vested In Period Fair Value 1				$ 10.1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term				9 years 10 months 24 days
Non-qualified Stock Option [Member]
Stockholders Equity Note [Line Items]
Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Grants In Period, Gross				220,000
Share-based Compensation Arrangement by Share-based Payment Award, Description				one-third will vest on the first anniversary of the date of grant, March 8, 2019; and the remaining two-thirds will vest in 24 equal monthly installments, with the option becoming fully vested on March 8, 2021
Warrant [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term				2 years 4 months 24 days
Class of Warrant or Right, Outstanding				15,296
Common Stock [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				248,762
Employees [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		131,559
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
Chief Financial Officer and Chief Operating Officer [Member] \| Non-qualified Stock Option [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				3 years
Restricted Stock Units (RSUs) [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	120,000
2010 Stock Incentive Plan [Member]
Stockholders Equity Note [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number				585,584
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			793,440
2014 Stock Incentive Plan [Member]
Stockholders Equity Note [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number				3,336,988
Common Stock, Capital Shares Reserved for Future Issuance							4,160,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				181,078
2017 Stock Incentive Plan [Member]
Stockholders Equity Note [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number				437,550
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				362,450
Restricted Stock [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance				251,559	120,000

Collaboration Agreement - Additional Information (Details) - USD ($)		3 Months Ended
	Feb. 10, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue		$ 3,565,060	$ 684,369
Deferred Revenue,Amortization Period Over Service Tenure		10 years
Licenses Revenue	$ 50,000,000
Deferred Revenue, Current		$ 5,159,587		$ 5,229,227
Deferred Revenue, Noncurrent		39,323,844		40,555,708
Cost of Reimbursable Expense		200,000
Accounts receivable from collaboration		2,263,556		2,273,421
Revenue Recognition, Milestone Method, Description	the Company is eligible to receive variable consideration in the form of cost-sharing reimbursements, up to approximately $630 million in related to seven development milestones and up to approximately $2.15 billion in related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications
Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue		1,300,000	700,000
Deferred Revenue, Current	$ 5,000,000	5,200,000		5,200,000
Deferred Revenue, Noncurrent		39,300,000		$ 40,600,000
Cost of Reimbursable Expense		2,300,000	$ 0
Revenue Recognition, Multiple-deliverable Arrangements, Determination of Selling Price, Amount		12,500,000
Deferred Revenue		$ 50,000,000
Allergan Pharmaceuticals International Limited [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Description Of Agree To Share Development Cost	In the event any pre-POC development costs exceed $75 million in the aggregate, the Company may elect either (a) to fund of such costs in excess of $75 million or (b) to allow Allergan to deduct from future development milestone payments of the development costs funded by Allergan in excess of $75 million plus a premium of 25%.
Proceeds From Upfront Payment	$ 50,000,000
Agreed To Share Maximum Amount Development Cost	$ 75,000,000
Revenue Recognition, Milestone Method, Description	the Company is eligible to receive up to approximately $630 million in payments related to seven development milestones and up to approximately $2.15 billion in payments related to 12 commercial development and sales milestones in connection with the successful development and commercialization of licensed compounds for up to six different indications

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments and Contingencies Disclosure [Line Items]
Operating Leases, Rent Expense	$ 400,000	$ 300,000
Equipment Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating Leases, Rent Expense	304,000	$ 182,000
Operating Leases, Future Minimum Payments Due	$ 2,600,000
Maximum [Member] \| Equipment Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating Lease Expiration Year	2021
Minimum [Member] \| Equipment Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating Lease Expiration Year	2017