Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 09, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Trading Symbol	CUE
Entity Registrant Name	Cue Biopharma, Inc.
Entity Central Index Key	0001645460
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		20,130,766

Condensed Balance Sheets (Unaudited) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 53,102,000	$ 63,534,000
Certificate of deposit	50,000	50,000
Research and development contract advances	1,383,000	852,000
Prepaid expenses and other current assets	884,000	403,000
Deposits, short-term	510,000	226,000
Total current assets	55,929,000	65,065,000
Property and equipment, net	2,423,000	1,691,000
Trademark	175,000	175,000
Long-term service contract	23,000	23,000
Deposits	776,000
Total assets	59,326,000	66,954,000
Current liabilities:
Accounts payable and accrued expenses	1,166,000	1,331,000
Accrued compensation and related expenses	259,000	857,000
Research and development collaboration agreement deferred credit	2,309,000	2,500,000
Research and development contract liabilities	341,000	623,000
Deferred rent	9,000	36,000
Total liabilities	4,084,000	5,347,000
Commitments and contingencies
Stockholders’ equity:
Preferred Stock, $0.001 par value; 10,000,000 shares authorized and 0 shares issued and outstanding at March 31, 2018 and December 31, 2017
Common stock, $0.001 par value; 50,000,000 shares authorized; 20,130,766 and 19,459,194 shares issued and outstanding, at March 31, 2018 and December 31, 2017, respectively	20,000	19,000
Common stock to be issued		1,000
Additional paid in capital	95,566,000	94,408,000
Accumulated deficit	(40,344,000)	(32,821,000)
Total stockholders’ equity	55,242,000	61,607,000
Total liabilities and stockholders’ equity	$ 59,326,000	$ 66,954,000

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares 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	20,130,766	19,459,194
Common stock, shares outstanding	20,130,766	19,459,194

Condensed Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses:
General and administrative	$ 1,703	$ 889
Research and development	5,819	2,461
Total operating expenses	7,522	3,350
Loss from operations	(7,522)	(3,350)
Other income (expense):
Other income (expense), net	(1)
Total other income (expense)	(1)
Net loss	$ (7,523)	$ (3,350)
Net loss per share basic and diluted	$ (0.37)	$ (0.31)
Weighted average common shares outstanding, basic and diluted	20,064	10,636

Condensed Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (7,523,000)	$ (3,350,000)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	167,000	67,000
Stock-based compensation expense	1,158,000	543,000
Deferred rent	(27,000)	(27,000)
Changes in operating assets and liabilities:
Research and development contract advances	(531,000)	(423,000)
Prepaid expenses and other current assets	(481,000)	(20,000)
Deposits	(1,060,000)	(101,000)
Accounts payable and accrued expenses	(390,000)	(76,000)
Accrued compensation and related expenses	(599,000)	(77,000)
Research and development contract liabilities	(282,000)
Research and development agreement deferred credits	(191,000)
Net cash used in operating activities	(9,759,000)	(3,464,000)
Cash flows from investing activities
Purchases of property and equipment	(673,000)	(556,000)
Net cash used in investing activities	(673,000)	(556,000)
Net increase (decrease) in cash	(10,432,000)	(4,020,000)
Cash at beginning of period	63,534,000	14,926,000
Cash at end of period	53,102,000	10,906,000
Supplemental disclosures of cash flow information:
Purchases of property and equipment in accounts payable and accrued expenses	$ 227,000	29,000
Accrual of deferred offering costs		$ 76,000

Organization and Basis of Presentation

3 Months Ended

Mar. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Basis of Presentation

1.	Organization and Basis of Presentation

Cue Biopharma, Inc. (the “Company”) was incorporated in the State of Delaware on December 31, 2014 under the name Imagen Biopharma, Inc., and completed its organization, formation and initial capitalization activities effective as of January 1, 2015. In October 2016, the Company changed its name to Cue Biopharma, Inc. The Company’s corporate office and research facilities are located in Cambridge, Massachusetts.

The Company is a pre-clinical biopharmaceutical company that is developing a novel and proprietary class of biologic drugs for the selective modulation of the human immune system to treat a broad range of cancers and autoimmune disorders.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Basis of Presentation

The accompanying condensed financial statements as of March 31, 2018, and for the three months ended March 31, 2018 and 2017, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) for Form 10-Q. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed financial statements reflect all adjustments which are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed financial statements should be read in conjunction with the financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 29, 2018.

The information presented in the condensed financial statements and related notes as of March 31, 2018, and for the three months ended March 31, 2018 and 2017, is unaudited. The December 31, 2017 condensed balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements.

Interim results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2018, or any future periods.

The Company is in the development stage and has incurred recurring losses and negative cash flows from operations. As of March 31, 2018, the Company had cash and cash equivalents of approximately $53,102,000. Management believes that current cash and cash equivalents on hand at March 31, 2018 should be sufficient to fund operations for at least the next twelve months from the date of issuance of these financial statements. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations and to fund increased research and development costs in order to seek approval for commercialization of its product candidates. The Company’s failure to raise capital as and when needed would have a negative impact on its financial condition and its ability to pursue its business strategies as this capital is necessary for the Company to perform the research and development activities required to develop the Company’s product candidates in order to generate future revenue streams.

Use of Estimates

The preparation of financial statements in conformity with United States Generally Accepted Accounting Principles (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates include the accounting for potential liabilities, the assumptions utilized in valuing stock-based compensation issued for services, the realization of deferred tax assets, and the impairment of long-lived assets and intangibles. Actual results could differ from those estimates.

Risks and Uncertainties

The Company’s operations are subject to a number of factors that may affect its operating results and financial condition. Such factors include, but are not limited to: the Company’s ability to determine candidates for clinical testing, the results of clinical testing and trial activities of the Company’s product candidates, the Company’s ability to obtain regulatory approval to market its product candidates, the Company’s intellectual property, competition from products manufactured and sold or being developed by other companies, the price of, and demand for, the Company’s product candidates if approved for sale, the Company’s ability to negotiate favorable licensing or other manufacturing and marketing agreements for its product candidates, and the Company’s ability to raise capital.

The Company currently has no commercially approved product candidates and there can be no assurance that the Company’s research and development programs will be successfully commercialized. Developing and commercializing a product requires significant time and capital and is subject to regulatory review and approval, as well as competition from other biotechnology and pharmaceutical companies. The Company operates in an environment of rapid change and is dependent upon the continued services of its employees and consultants and obtaining and protecting its intellectual property.

Cash Concentrations

The Company maintains its cash balances with a financial institution in Federally-insured accounts and may periodically have cash balances in excess of insurance limits. The Company maintains its accounts with a financial institution with a high credit rating. The Company has not experienced any losses to date and believes that it is not exposed to any significant credit risk on cash.

Restricted Cash

The Company purchased a $50,000 certificate of deposit to collateralize a credit card account with a commercial bank that was classified as short-term restricted cash as of March 31, 2018 and December 31, 2017.

Property and Equipment

Property and equipment is recorded at cost. Major improvements are capitalized, while maintenance and repairs are charged to expense as incurred. Gains and losses from disposition of property and equipment are included in income and expense when realized. Amortization of leasehold improvements is provided using the straight-line method over the shorter of the lease term or the useful life of the underlying assets. Depreciation of property and equipment is provided using the straight-line method over the following estimated useful lives:

Laboratory equipment		5 years
Computer and office equipment		3 years
Furniture and fixtures		3-8 years

The Company recognizes depreciation and amortization expense in general and administrative expenses and in research and development expenses in the Company’s statements of operations, depending on how each category of property and equipment is utilized in the Company’s business activities.

Research and Development Expenses

Research and development expenses consist primarily of compensation costs, fees paid to consultants, outside service providers and organizations (including research institutes at universities), facility costs, and development and clinical trial costs with respect to the Company’s product candidates.

Research and development expenses incurred under contracts are expensed ratably over the life of the underlying contracts, unless the achievement of milestones, the completion of contracted work, or other information indicates that a different expensing schedule is more appropriate. Other research and development expenses are charged to operations as incurred.

Payments made pursuant to research and development contracts are initially recorded as research and development contract advances in the Company’s balance sheet and then charged to research and development expenses in the Company’s statement of operations as those contract services are performed. Expenses incurred under research and development contracts in excess of amounts advanced are recorded as research and development contract liabilities in the Company’s balance sheet, with a corresponding charge to research and development expenses in the Company’s statement of operations.

Nonrefundable advance payments for future research and development activities pursuant to an executory contractual arrangement are recorded as advances as described above. Nonrefundable advance payments are recognized as an expense as the related services are performed. The Company evaluates whether it expects the services to be rendered at each quarter end and year end reporting date. If the Company does not expect the services to be rendered, the advance payment is charged to expense. To the extent that a nonrefundable advance payment is for contracted services to be performed within 12 months from the reporting date, such advance is included in current assets; otherwise, such advance is included in non-current assets.

The Company evaluates the status of its research and development agreements and contracts, and the carrying amount of the related assets and liabilities, at each quarter end and year end reporting date, and adjusts the carrying amounts and their classification on the balance sheet as appropriate.

Research and Development Funding Arrangements

The Company’s proprietary biologics are at an early stage and will require substantial time and funding to continue development. There can be no assurances that any of the Company’s biologics will ultimately become commercially viable product candidates. In order to finance its research and development programs, the Company may periodically enter into collaboration agreements with third parties that provide funding for certain aspects of the Company’s ongoing research and development activities. The Company considers various factors in determining the appropriate accounting treatment for such collaboration agreements, including, among others, the risks of and costs associated with the research and development program being funded, the stage of development of the proprietary biologics subject to the research and development program, the likelihood at initiation that the collaboration arrangement will result in an economically successful outcome to the third party, the continuing involvement of the Company in the research and development program and the expenditure of the funds, the transfer of the financial risk associated with the research and development program to the third party, the intended use of the funds and any restrictions thereon, and the probability of any repayment obligations or other forms of consideration if the proprietary biologics subject to the research and development program are not successfully developed and commercialized.

In accordance with ASC 730-20-25-8, to the extent that a collaboration agreement results in a substantive and genuine transfer of financial risk to a third party funding source because any economic benefit that the third party may receive depends solely on the research and development program successfully developing commercially viable product candidates having future economic benefit (which is uncertain at the initiation of the collaboration agreement), the Company will account for such collaboration agreement as a contract to perform research and development services for a third party. The funds received from the third party under such a collaboration agreement will initially be recorded as a deferred credit in the Company’s balance sheet. As the related contractual research and development costs are incurred, the applicable amount of the deferred credit will be credited to operations and will be classified as an offset to such research and development costs in the Company’s statement of operations.

Patent Expenses

The Company is the exclusive worldwide licensee of, and has patent applications pending for, numerous domestic and foreign patents. Due to the significant uncertainty associated with the successful development of one or more commercially viable product candidates based on the Company’s research efforts and any related patent applications, all patent costs, including patent-related legal fees, filing fees and other costs are charged to operations as incurred. For the three months ended March 31, 2018 and 2017, patent expenses were $117,000 and $109,000, respectively. Patent expenses are included in general and administrative expenses in the Company’s statement of operations.

Licensing Fees and Costs

Licensing fees and costs consist primarily of costs relating to the acquisition of the Company’s license agreement with Einstein, including related royalties, maintenance fees, milestone payments and product development costs. Licensing fees and costs are charged to operations as incurred.

Long-Lived Assets

The Company reviews long-lived assets, consisting of property and equipment, for impairment at each fiscal year end or when events or changes in circumstances indicate the carrying value of these assets may exceed their current fair values. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized for the amount by which the carrying amount of the asset exceeds the fair value of the assets. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The Company has not historically recorded any impairment to its long-lived assets. In the future, if events or market conditions affect the estimated fair value to the extent that a long-lived asset is impaired, the Company will adjust the carrying value of these long-lived assets in the period in which the impairment occurs.

Rent Expense and Deferred Rent Liability

Operating lease agreements which contain provisions for future rent increases or periods in which rent payments are reduced or abated are recorded in monthly rent expense in the amount of the total payments over the lease term divided by the number of months of the lease term. The difference between rent expense recorded and the amount paid is credited or charged to a deferred rent liability account. The current portion of deferred rent is included in current liabilities, and the remaining amount is shown in the balance sheet as a non-current liability. Accordingly, rent expense is recorded on a straight-line basis.

Stock-Based Compensation

The Company periodically issues stock options to officers, directors, employees, Scientific and Clinical Advisory Board members, non-employees and consultants for services rendered. Such issuances vest and expire according to terms established at the issuance date.

Stock-based payments to officers, directors and employees, including grants of employee stock options, are recognized in the financial statements based on their grant date fair values. Stock option grants, which are generally time-vested, are measured at the grant date fair value and charged to operations on a straight-line basis over the vesting period. The fair value of stock options is determined utilizing the Black-Scholes option-pricing model, which is affected by several variables, including the risk-free interest rate, the expected dividend yield, the life of the equity award, the exercise price of the stock option as compared to the fair value of the common stock on the grant date, and the estimated volatility of the common stock over the term of the equity award.

Stock options granted to members of the Company’s Scientific and Clinical Advisory Board, non-employees and outside consultants are revalued each reporting period to determine the amount to be recorded as an expense in the respective period. As the stock options vest, they are valued on each vesting date and an adjustment is recorded for the difference between the value already recorded and the value on the date of vesting.

The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Until the Company has established a trading market for its common stock, estimated volatility is based on the average historical volatilities of comparable public companies in a similar industry. The expected dividend yield is based on the current yield at the grant date; the Company has never declared or paid dividends and has no plans to do so for the foreseeable future. As permitted by Staff Accounting Bulletin No. 107, due to the Company’s lack of trading history and option activity, management utilizes the simplified method to estimate the expected term of options at the date of grant. The exercise price is determined based on the fair value of the Company’s common stock at the date of grant. The Company accounts for forfeitures as they occur in accordance with ASU 2016-09, Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), and reverses previously recognized stock compensation costs in the period that the award is forfeited.

The Company recognizes the fair value of stock-based compensation in general and administrative expenses and in research and development expenses in the Company’s statement of operations, depending on the type of services provided by the recipient of the equity award. The Company issues new shares of common stock to satisfy stock option exercises.

Earnings (Loss) Per Share

The Company’s computation of earnings (loss) per share (“EPS”) for the respective periods includes basic and diluted EPS. Basic EPS is measured as the income (loss) attributable to common stockholders divided by the weighted average number of common shares outstanding for the period. Diluted EPS is similar to basic EPS but presents the dilutive effect on a per share basis of potential common shares that would result from the exercise of outstanding stock options and warrants as if they had been exercised at the beginning of the periods presented, or issuance date, if later. Potential common shares that have an anti-dilutive effect (i.e., those that increase income per share or decrease loss per share) are excluded from the calculation of diluted EPS. Basic and diluted loss per common share is the same for all periods presented because all outstanding stock options and warrants are anti-dilutive.

At March 31, 2018 and 2017, the Company excluded the outstanding securities summarized below, which entitle the holders thereof to acquire shares of common stock, from its calculation of earnings per share, as their effect would have been anti-dilutive.

	March 31,
(in thousands)	2018		2017
Common stock warrants		1,252		370
Common stock options		2,757		1,836
Total		4,009		2,206

Recent Accounting Pronouncements and Adopted Standards

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 eliminates transaction- and industry-specific revenue recognition guidance under current GAAP and replaces it with a principle based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The FASB has issued ASU 2016-08, ASU 2016-10, ASU 2016-11, ASU 2016-12, and ASU 2016-20, all of which clarify certain implementation guidance within ASU 2014-09. ASU 2014-09 is effective for reporting periods beginning after December 15, 2017, with early adoption permitted. Entities are able to transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. The Company adopted the provisions of ASU 2014-09 as of January 1, 2018. As the Company is unlikely to generate any sustainable operating revenues in the next several years, the adoption of ASU 2014-09 did not have any impact on the Company’s financial statement presentation or disclosures.

In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 requires a lessee to record a right-of-use asset and a corresponding lease liability, initially measured at the present value of the lease payments, on the balance sheet for all leases with terms longer than 12 months, as well as the disclosure of key information about leasing arrangements. ASU 2016-02 requires recognition in the statement of operations of a single lease cost, calculated so that the cost of the lease is allocated over the lease term, generally on a straight-line basis. ASU 2016-02 requires classification of all cash payments within operating activities in the statement of cash flows. Disclosures are required to provide the amount, timing and uncertainty of cash flows arising from leases. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted. The Company will adopt the provisions of ASU 2016-02 in the quarter beginning January 1, 2019. The Company generally does not finance purchases of property and equipment, but does lease its operating facilities. While the Company is continuing to assess the potential impact of ASU 2016-02, it currently expects that most of its lease commitments will be subject to ASU 2016-02 and accordingly, upon adoption will be recognized as lease liabilities and right-of-use assets in the Company’s balance sheet.

In May 2017, the FASB issued Accounting Standards Update No. 2017-09, Compensation-Stock Compensation (Topic 718); Scope of Modification Accounting (“ASU 2017-09”). 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 this ASU are effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The ASU is applied prospectively on and after the effective date. This standard did not have a material effect on the Company’s financial statements.

In July 2017, the FASB issued Accounting Standards Update No. 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features; (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). ASU 2017-11 allows companies to exclude a down round feature when determining whether a financial instrument (or embedded conversion feature) is considered indexed to the entity’s own stock. As a result, financial instruments (or embedded conversion features) with down round features may no longer be required to be accounted for as derivative liabilities. A company will recognize the value of a down round feature only when it is triggered and the strike price has been adjusted downward. For equity-classified freestanding financial instruments, an entity will treat the value of the effect of the down round as a dividend and a reduction of income available to common shareholders in computing basic earnings per share. For convertible instruments with embedded conversion features containing down round provisions, entities will recognize the value of the down round as a beneficial conversion discount to be amortized to earnings. ASU 2017-11 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The guidance in ASU 2017-11 can be applied using a full or modified retrospective approach. The adoption of ASU 2017-11 is not currently expected to have any impact on the Company’s financial statement presentation or disclosures.

Management does not believe that any other recently issued, but not yet effective, authoritative guidance, if currently adopted, would have a material impact on the Company’s financial statement presentation or disclosures.

Property and Equipment

3 Months Ended

Mar. 31, 2018

Property Plant And Equipment [Abstract]

Property and Equipment

3.	Property and Equipment

Property and equipment as of March 31, 2018 and December 31, 2017 consisted of the following:

	March 31, 2018			December 31, 2017
	(in thousands)
Computer and office equipment	$	129		$	83
Laboratory equipment		3,058			2,205
Furniture and fixtures		10			10
Leasehold improvements		54			54
		3,251			2,352
Less: Accumulated depreciation		(828	)		(661	)
Total property and equipment, net	$	2,423		$	1,691

Depreciation expense for the three months ended March 31, 2018 and 2017 was approximately $167,000 and $67,000, respectively. During the three months ended March 31, 2018 and 2017, there were no disposals of property and equipment..

Stock-Based Compensation and Warrants

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation and Warrants

4.	Stock-Based Compensation and Warrants

For stock options requiring an assessment of value during the three months ended March 31, 2018, the fair value of each stock option award was estimated using the Black-Scholes option-pricing model utilizing the following assumptions:

		March 31, 2018
Risk-free interest rate		2.43 to 2.62%
Expected dividend yield		0%
Expected volatility		82.0-83.0%
Expected life		3.2 to 7.0 years

A summary of stock option activity for the three months ended March 31, 2018 is as follows:

	Number of Shares (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in Years)
Stock options outstanding at December 31, 2017		2,732	$	4.07		5.76
Granted		25	$	16.65
Exercised		—	$	—
Cancelled		—	$	—
Stock options outstanding at March 31, 2018		2,757	$	4.18		5.52
Stock options exercisable at March 31, 2018		818	$	3.13		4.95

The Company recognized approximately $1,158,000 and $543,000 in stock-based compensation during the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, total unrecognized stock-based compensation was approximately $10,219,000, which is expected to be recognized as an operating expense in the Company’s statement of operations through June 2022.

The intrinsic value of exercisable but unexercised in-the-money stock options at March 31, 2018 was approximately $8,941,000, based on a fair value of $14.05 per share on March 29, 2018.

Stock-based compensation for the three months ended March 31, 2018 and 2017 was included in the statement of operations as follows:

	March 31,
(in thousands)	2018		2017
General and administrative	$	380	$	227
Research and development		778		316
Total	$	1,158	$	543

The Company had approximately 1,252,000 of outstanding and exercisable common stock warrants at March 31, 2018. The intrinsic value of exercisable but unexercised in-the-money common stock warrants at March 31, 2018 was approximately $8,323,000 based on a fair value of $14.05 per share on March 29, 2018.

Related Party Transactions

3 Months Ended

Mar. 31, 2018

Related Party Transactions

5.	Related Party Transactions

The former interim Chief Financial Officer of the Company, who is also the Chief Financial Officer of MDB, a related party, has been compensated at a rate of $6,000 per month, reflecting an aggregate charge to operations for each of the three months ended March 31, 2018 and 2017 of $18,000.

During 2015, the Company entered into a license agreement, (the “Einstein License”), with the Albert Einstein College of Medicine, (“Einstein”) for certain patent rights (the “Patents”) relating to the Company’s core technology platform for the engineering of biologics to control T-cell activity, precision, immune-modulatory drug candidates, and two supporting technologies that enable the discovery of costimulatory signaling molecules (ligands) and T-cell targeting peptides. On July 31, 2017, the Company entered into an amended and restated license agreement which modified certain obligations of the parties under the Einstein License. For each of the three months ended March 31, 2018 and 2017, the Company incurred approximately $12,500 in fees and expenses to Einstein in relation to this license.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6.	Commitments and Contingencies

Einstein License and Service Agreement

During 2015, the Company entered into a license agreement, (the “Einstein License”), with the Albert Einstein College of Medicine, (Einstein) for certain patent rights (the “Patents”) relating to the Company’s core technology platform for the engineering of biologics to control T-cell activity, precision, immune-modulatory drug candidates, and two supporting technologies that enable the discovery of costimulatory signaling molecules (ligands) and T-cell targeting peptides. The Company’s remaining commitments with respect to this agreement are based on the attainment of future milestones.

Agreements with Catalent

On March 7, 2017, the Company entered into an agreement with Catalent for Catalent to provide services on a sequential milestone basis with respect to the development and manufacture of the Company’s lead drug candidate, CUE-101. The services under the agreement are designed to support the preparation and filing of an Investigational New Drug Application with the United States Food and Drug Administration to allow for the commencement of a Phase 1 clinical trial of CUE-101 in the United States. The Company incurred total direct costs under this agreement aggregating $1.2 million during the three months ended March 31, 2018 and currently estimates that it will incur an additional $3.2 of such costs during the year ended December 31, 2018. Certain of these payments will consist of nonrefundable advance payments for which the Company anticipates receiving the contracted services within 12 months from the date of payment. Management periodically reviews and updates the project’s estimated budget and timeline.

Collaboration Agreement with Merck

On November 14, 2017, the Company entered into an Exclusive Patent License and Research Collaboration Agreement (the “Collaboration Agreement”) with Merck Sharp & Dohme Corp. (“Merck”) for a partnership to research and develop certain of the Company’s proprietary biologics that target certain autoimmune disease indications (the “Initial Indications”). We view this Collaboration Agreement as a component of our development strategy since it will allow us to advance our autoimmune programs in partnership with a world class pharmaceutical company, while also continuing our focus on our more advanced cancer programs. The research program outlined in the Collaboration Agreement entails (1) our research, discovery and development of certain CUE Biologics™ drug candidates up to the point of demonstration of certain biologically relevant effects (“Proof of Mechanism”) and (2) the further development by Merck of the CUE Biologics™ drug candidates that have demonstrated Proof of Mechanism (the “Proposed Product Candidates”) up to the point of demonstration of all or substantially all of the properties outlined in such Proposed Product Candidates’ profiles as described in the Collaboration Agreement.

For the purposes of this collaboration, the Company granted to Merck under the Collaboration Agreement an exclusive license under certain of is patent rights, including a sublicense of patent rights licensed from Einstein, to the extent applicable to the specific CUE Biologics™ that are elected to be developed by Merck. From the effective date of the Collaboration Agreement until the earlier of (i) the first achievement of Proof of Mechanism for a CUE Biologics™ drug candidate or (ii) 18 months after the Company notifies the joint steering committee that the first Product Candidate has been synthesized under the research program, the Company is required to forebear from researching, developing or licensing to a third party rights related to any CUE Biologics™ drug candidate for the treatment of autoimmune diseases other than pursuant to the Collaboration Agreement. In addition, so long as Merck continues product development on a Proposed Product Candidate, the Company is restricted from conducting any development activities within the Initial Indication covered by such Proposed Product Candidate other than pursuant to the Collaboration Agreement. The Company is not required to forbear at any time, however, from developing other CUE Biologics™ for use in therapeutic areas other than autoimmune diseases, e.g., for use in treating cancer or infectious diseases.

In exchange for the licenses and other rights granted to Merck under the Collaboration Agreement, Merck paid to the Company a $2.5 million nonrefundable up-front payment. Additionally, the Company may be eligible to receive funding in developmental milestone payments, as well as tiered royalties, if all research, development, regulatory and commercial milestones agreed upon by both parties are successfully achieved. Excluding the up-front payment described above, the Company is eligible to earn up to $101 million for the achievement of certain research and development milestones, $120 million for the achievement of certain regulatory milestones and $150 million for the achievement of certain commercial milestones, in addition to tiered royalties on sales, if all pre-specified milestones associated with multiple products across the primary disease indication areas are achieved. The Collaboration Agreement requires the Company to use the first $2.7 million of milestone payments we receive under the agreement to fund contract research. The amount of the royalty payments is a percentage of product sales ranging in the single digits based on the amount of such sales. For the three months ended March 31, 2018, the Company recorded approximately $191,000 in direct costs to the non-refundable up-front payment.

The term of the Collaboration Agreement extends until the expiration of all royalty obligations following a product candidate’s receipt of marketing authorization, at which point Merck’s licenses and sublicenses granted under the agreement shall become fully paid-up, perpetual licenses and sublicenses, as applicable. Royalties on each product subject to the Collaboration Agreement shall continue on a country-by-country basis until the expiration of the later of: (1) the last-to-expire patent claiming the compound on which such product is based and (2) a period of ten years after the first commercial sale of such product in such country.

Notwithstanding the foregoing, Merck may terminate the Collaboration Agreement at any time upon 30 days’ notice to the Company. The Collaboration Agreement may also be terminated by either party if the other party is in breach of its obligations thereunder and fails to cure such breach within 90 days after notice or by either party if the other party files for bankruptcy or other similar insolvency proceedings.

Leased Facilities

On July 29, 2015, the Company entered into an operating lease agreement for its laboratory space for the period from August 1, 2015 through April 30, 2018. The lease contained escalating payments during the lease period. The Company records monthly rent expense on the straight-line basis, equal to the total of the lease payments over the lease term divided by the number of months of the lease term.

On November 14, 2016, the Company entered into an amended lease agreement that provided the Company with additional laboratory space. This amendment was effective beginning December 1, 2016 and expired on April 30, 2018.

On July 30, 2015, the Company entered into an operating lease agreement, as amended, for dedicated vivarium space for the period from August 1, 2015 through March 31, 2018. The operating lease agreement contained an option to increase the amount of space leased for an additional cost.

On January 16, 2018, the Company entered into an amended lease agreement that provided the Company with additional laboratory space. This amendment was effective beginning on January 16, 2018 and expired on April 30, 2018.

On January 18, 2018, the Company entered into an operating lease agreement for its laboratory and office space at 21 Erie St. Cambridge, Massachusetts for the period from May 1, 2018 through April 30, 2021.The lease contains escalating payments during the lease period. Upon execution of this lease agreement the Company prepaid three months of rent which will be held in escrow and credited against future rents.

Future minimum lease payments under these leases at March 31, 2018 are as follows:

Year	(in thousands)
2018	$	2,595
2019		3,752
2020		4,661
2021		1,553
Total	$	12,561

Total rent expense, excluding dedicated vivarium space, of approximately $670,000 and $493,000 was included in the statement of operations for the three months ended March 31, 2018 and 2017, respectively.

Legal Contingencies

The Company may be subject to various legal proceedings from time to time as part of its business. As of March 31, 2018, the Company was not a party to any legal proceedings or threatened legal proceedings, the adverse outcome of which, individually or in the aggregate, would have a material adverse effect on its business, financial condition or results of operations.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation

Interim results for the three months ended March 31, 2018 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2018, or any future periods.

Use of Estimates

Risks and Uncertainties

Cash Concentrations

Restricted Cash

Property and Equipment

Laboratory equipment		5 years
Computer and office equipment		3 years
Furniture and fixtures		3-8 years

Research and Development Expenses

Research and Development Funding Arrangements

Patent Expenses

Licensing Fees and Costs

Long-Lived Assets

Rent Expense and Deferred Rent Liability

Stock-Based Compensation

Earnings (Loss) Per Share

	March 31,
(in thousands)	2018		2017
Common stock warrants		1,252		370
Common stock options		2,757		1,836
Total		4,009		2,206

Recent Accounting Pronouncements and Adopted Standards

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Estimated Useful Lives of Assets

Depreciation of property and equipment is provided using the straight-line method over the following estimated useful lives:

Laboratory equipment		5 years
Computer and office equipment		3 years
Furniture and fixtures		3-8 years

Schedule of Anti-dilutive Securities Excluded from Computation of Earnings Per Share

	March 31,
(in thousands)	2018		2017
Common stock warrants		1,252		370
Common stock options		2,757		1,836
Total		4,009		2,206

Property and Equipment (Tables)

3 Months Ended

Mar. 31, 2018

Property Plant And Equipment [Abstract]

Summary of Property and Equipment

Property and equipment as of March 31, 2018 and December 31, 2017 consisted of the following:

	March 31, 2018			December 31, 2017
	(in thousands)
Computer and office equipment	$	129		$	83
Laboratory equipment		3,058			2,205
Furniture and fixtures		10			10
Leasehold improvements		54			54
		3,251			2,352
Less: Accumulated depreciation		(828	)		(661	)
Total property and equipment, net	$	2,423		$	1,691

Stock-Based Compensation and Warrants (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Estimated Fair Value of Each Stock Option Award

		March 31, 2018
Risk-free interest rate		2.43 to 2.62%
Expected dividend yield		0%
Expected volatility		82.0-83.0%
Expected life		3.2 to 7.0 years

Summary of Stock Option Activity

A summary of stock option activity for the three months ended March 31, 2018 is as follows:

	Number of Shares (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in Years)
Stock options outstanding at December 31, 2017		2,732	$	4.07		5.76
Granted		25	$	16.65
Exercised		—	$	—
Cancelled		—	$	—
Stock options outstanding at March 31, 2018		2,757	$	4.18		5.52
Stock options exercisable at March 31, 2018		818	$	3.13		4.95

Schedule of Stock-Based Compensation Included in Statement of Operations

Stock-based compensation for the three months ended March 31, 2018 and 2017 was included in the statement of operations as follows:

	March 31,
(in thousands)	2018		2017
General and administrative	$	380	$	227
Research and development		778		316
Total	$	1,158	$	543

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments for Operating Lease

Future minimum lease payments under these leases at March 31, 2018 are as follows:

Year	(in thousands)
2018	$	2,595
2019		3,752
2020		4,661
2021		1,553
Total	$	12,561

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) Product	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 53,102,000	$ 10,906,000	$ 63,534,000	$ 14,926,000
Number of commercial approved product candidates \| Product	0
General and Administrative Expense
Summary Of Significant Accounting Policies [Line Items]
Patent expenses	$ 117,000	$ 109,000
Certificate of Deposit
Summary Of Significant Accounting Policies [Line Items]
Short-term restricted cash	$ 50,000		$ 50,000

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Details)	3 Months Ended
	Mar. 31, 2018
Laboratory Equipment
Property Plant And Equipment [Line Items]
Estimated useful lives	5 years
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Estimated useful lives	3 years
Furniture and Fixtures \| Minimum
Property Plant And Equipment [Line Items]
Estimated useful lives	3 years
Furniture and Fixtures \| Maximum
Property Plant And Equipment [Line Items]
Estimated useful lives	8 years

Summary of Significant Accounting Policies - Schedule of Anti-dilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Thousands	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	4,009	2,206
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1,252	370
Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,757	1,836

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 3,251	$ 2,352
Less: Accumulated depreciation	(828)	(661)
Total property and equipment, net	2,423	1,691
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	129	83
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	3,058	2,205
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	10	10
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 54	$ 54

Property and Equipment - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation	$ 167,000	$ 67,000
Disposals of property and equipment	$ 0	$ 0

Stock-Based Compensation and Warrants - Schedule of Estimated Fair Value of Each Stock Option Award (Details)	3 Months Ended
	Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	2.43%
Risk-free interest rate, maximum	2.62%
Expected dividend yield	0.00%
Expected volatility, minimum	82.00%
Expected volatility, maximum	83.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	3 years 2 months 12 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	7 years

Stock-Based Compensation and Warrants - Summary of Stock Option Activity (Details) - $ / shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Number of Shares, Outstanding Beginning Balance	2,732
Number of Shares, Granted	25
Number of Shares, Outstanding Ending Balance	2,757	2,732
Number of Shares, Exercisable	818
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 4.07
Weighted Average Exercise Price, Granted	16.65
Weighted Average Exercise Price, Outstanding Ending Balance	4.18	$ 4.07
Weighed Average Exercise Price, Exercisable	$ 3.13
Weighted Average Remaining Contractual Life (in Years)	5 years 6 months 7 days	5 years 9 months 3 days
Weighted Average Remaining Contractual Life (in Years), Exercisable	4 years 11 months 12 days

Stock-Based Compensation and Warrants - Additional Information (Details) - USD ($)		3 Months Ended
	Mar. 29, 2018	Mar. 31, 2018	Mar. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation		$ 1,158,000	$ 543,000
Unrecognized stock-based compensation		10,219,000
Intrinsic value of exercisable stock options		$ 8,941,000
Intrinsic value of exercisable fair value per share	$ 14.05
Warrant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock warrants outstanding		1,252,000
Common stock warrants exercisable		1,252,000
Intrinsic value of common stock warrants		$ 8,323,000
Fair value of common stock	$ 14.05

Stock-Based Compensation and Warrants - Schedule of Stock-Based Compensation Included in Statement of Operations (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,158,000	$ 543,000
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	380,000	227,000
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 778,000	$ 316,000

Related Party Transactions - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2015 SupportingTechnology
Einstein License
Related Party Transaction [Line Items]
Number of supporting technologies \| SupportingTechnology			2
Patent expenses	$ 12,500	$ 12,500
Chief Financial Officer \| MDB
Related Party Transaction [Line Items]
Monthly compensation payable to officer	6,000
Aggregate compensation payable to officer	$ 18,000	$ 18,000

Commitments and Contingencies - Additional Information (Details)					3 Months Ended		12 Months Ended
	May 01, 2018	Jan. 16, 2018	Nov. 14, 2017 USD ($)	Dec. 01, 2016	Mar. 31, 2018 USD ($) SupportingTechnology	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)
Commitments And Contingencies [Line Items]
Rent expense					$ 670,000	$ 493,000
Amended Lease Agreement
Commitments And Contingencies [Line Items]
Lease agreement effective date		Jan. 16, 2018		Dec. 01, 2016
Lease expiration date		Apr. 30, 2018		Apr. 30, 2018
Operating Lease Agreement \| Sebsequent Event
Commitments And Contingencies [Line Items]
Lease agreement effective date	May 01, 2018
Lease expiration date	Apr. 30, 2021
Einstein License and Service Agreement \| Einstein
Commitments And Contingencies [Line Items]
Number of supporting technology \| SupportingTechnology					2
Agreements with Catalent \| Catalent \| Services on Development and Manufacture of Lead Drug Candidate
Commitments And Contingencies [Line Items]
Total direct costs under agreement					$ 1,200,000
Anticipated contracted services to be received, period from date of payment					12 months
Agreements with Catalent \| Catalent \| Scenario, Forecast \| Services on Development and Manufacture of Lead Drug Candidate
Commitments And Contingencies [Line Items]
Total direct costs under agreement							$ 3,200,000
Collaboration Agreement with Merck \| Einstein
Commitments And Contingencies [Line Items]
Collaborative arrangements expiration period			10 years
Collaboration Agreement with Merck \| Merck
Commitments And Contingencies [Line Items]
Up front non refundable payment			$ 2,500,000
Achievement of certain research and development milestones			120,000,000
Achievement of certain commercial milestones			150,000,000
Milestone payments received			$ 2,700,000
Direct costs related to non-refundable up-front payments					$ 191,000
Collaboration agreement termination terms days ff written notice period			30 days
Collaboration agreement termination terms days of written notice cure breach before termination days			90 days
Collaboration Agreement with Merck \| Merck \| Maximum
Commitments And Contingencies [Line Items]
Eligible to earn achievement of certain research and development milestones			$ 101,000,000

Commitments and Contingencies - Schedule of Future Minimum Lease Payments on Operating Leases (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2018	$ 2,595
2019	3,752
2020	4,661
2021	1,553
Total	$ 12,561

Organization and Basis of Presentation - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
State of incorporation	Delaware
Date of incorporation	Dec. 31, 2014