The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the fair value hierarchy classification of such fair values as of December 31, 2022 and 2021 (in thousands):

10. Collaboration and License Agreements

Acceleron Collaboration Agreement

On December 20, 2019, the Company entered into the Acceleron Collaboration Agreement to identify biological targets to modulate specific pathways associated with a targeted indication within the pulmonary disease space (the “Indication”). Under the terms of the Acceleron Collaboration Agreement, the Company granted Acceleron an exclusive worldwide license under certain intellectual property rights to make, have made, use, sell, have sold, import, export, distribute and have distributed, market, have marketed, promote, have promoted, or otherwise exploit molecules and products directed against or expressing certain biological targets identified by the Company for the treatment, prophylaxis, or diagnosis of the Indication.

On June 3, 2022, Acceleron notified the Company of its termination of the Acceleron Collaboration Agreement for convenience, which became effective 120 days after the Company's receipt of the notice, or October 1, 2022.

Pursuant to a mutually agreed research plan, the Company was responsible for performing assay screening and related research activities to identify and validate potential biological targets for further research, in order to support the development, manufacture and commercialization of product candidates by Acceleron. Upon completion of the research activities, the Company delivered a data package to Acceleron with respect to the biological targets identified by the Company in the conduct of the research activities for the treatment, prophylaxis, or diagnosis of the Indication. As provided for under the exclusive worldwide license that was conveyed at the inception of the arrangement, Acceleron had the right to designate a specified number of the biological targets identified by the Company for Acceleron’s research, development, manufacture and commercialization of products or molecules directed to such targets for the treatment, prophylaxis, or diagnosis of the Indication (the “Targets”). Acceleron did not designate any Targets prior to the notice of termination from Acceleron.

The Company received a non-refundable upfront payment of $10.0 million in December 2019 upon the execution of the Acceleron Collaboration Agreement. The Company was entitled to research milestone payments of up to $18.5 million in the aggregate upon achievement of specified research milestones, development milestone payments of up to $202.5 million in the aggregate upon achievement of specified clinical and regulatory milestones, and sales milestones payments of up to $217.5 million in the aggregate upon the achievement of certain aggregate annual worldwide net sales milestones for certain products directed to a Target that have achieved such milestones. Prior to the notice of termination from Acceleron, the Company achieved $2.0 million of specified research milestones. In addition, the Company was entitled to tiered royalties ranging from a mid single-digit percentage to a low double-digit percentage on Acceleron’s annual worldwide net sales of products directed to any Target, subject to reduction in specified circumstances. The Company was also entitled to receive reimbursement from Acceleron for research costs incurred under the research plan, including internal and external costs.

Accounting Analysis

Identification of the Contract

The Company assessed the Acceleron Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606.

Identification of the Promises and Performance Obligations

The Company determined that the Acceleron Collaboration Agreement contained the following promises: (i) an exclusive worldwide license under certain intellectual property rights, including rights to a specified number of biological targets identified by the Company for the treatment, prophylaxis, or diagnosis of a targeted indication within the pulmonary disease space that was conveyed at the inception of the arrangement (the “License”), (ii) research services to identify and validate potential biological targets (the “Research Services”), and (iii) participation in the joint steering committee (the “JSC”).

The Company assessed the above promises and concluded that the License is not capable of being distinct from the Research Services given that the License has limited value without the performance of the Research Services and the Research Services could only be performed by the Company due to their specialized nature. Therefore, the Company concluded that the License and the Research Services represented a single combined performance obligation.

The Company also assessed the participation on the JSC and concluded that the promise was quantitatively and qualitatively immaterial in the context of the Acceleron Collaboration Agreement. Accordingly, the Company disregarded its participation on the JSC as a performance obligation.

Determination of the Transaction Price

The Company received a non-refundable upfront payment of $10.0 million upon the execution of the Acceleron Collaboration Agreement, which the Company included in the transaction price. In December 2020, the Company achieved $2.0 million of specified research milestones associated with the Acceleron Collaboration Agreement, which the Company included in the transaction price. The Company has constrained the variable consideration associated with the unachieved milestone payments as of the date that the Company received notice of termination from Acceleron and has excluded the unachieved milestone payments from the transaction price.

The Company also included in the transaction price the amount of costs to be reimbursed for the Research Services.

Prior to the receipt of notice of termination from Acceleron, the Company reassessed the transaction price at the end of each reporting period and as uncertain events were resolved or other changes in circumstances occurred, and, if necessary, adjusted its estimate of the transaction price. There was no change in the amount of variable consideration constrained during the year ended December 31, 2022.

Allocation of the Transaction Price to Performance Obligations

As noted above, the Company identified a single performance obligation associated with the Acceleron Collaboration Agreement. Therefore, the Company allocated the entire amount of the transaction price to the identified single performance obligation.

Recognition of Revenue

The Company recognized revenue related to the Acceleron Collaboration Agreement over time as the Research Services are rendered. The Company concluded that an input method was a representative depiction of the transfer of services under the Acceleron Collaboration Agreement. Prior to the receipt of notice of termination from Acceleron, the method of measuring progress towards the delivery of the services incorporated actual cumulative internal and external costs incurred relative to total internal and external costs expected to be incurred to satisfy the performance obligation. The period over which total costs was estimated reflected the Company’s estimate of the period over which it would perform the Research Services. Changes in estimates of total internal and external costs expected to be incurred were recognized in the period of change as a cumulative catch-up adjustment.

During the year ended December 31, 2022, the Company recognized $1.0 million of collaboration revenue associated with the Acceleron Collaboration Agreement, which includes $0.6 million of revenue recognized that was included in deferred revenue as of December 31, 2021. During the year ended December 31, 2021, the Company recognized $9.6 million of collaboration revenue associated with the Acceleron Collaboration Agreement, which includes $7.3 million of revenue recognized that was included in deferred revenue as of December 31, 2020. As of December 31, 2022 the Company recorded no deferred revenue associated with the Acceleron Collaboration Agreement. As of December 31, 2021 the Company recorded deferred revenue associated with the Acceleron Collaboration Agreement of $0.6 million, which was classified as either current or net of current portion in the accompanying consolidated balance sheets based on the period over which the revenue was expected to be recognized. The aggregate deferred revenue balance represents the aggregate amount of the transaction price allocated to the performance obligations that were unsatisfied as of December 31, 2021. As of December 31, 2022, the Company had received $4.9 million of cost reimbursement payments under the Acceleron Collaboration Agreement and $2.0 million associated with the achievement of specified research milestones. As of December 31, 2021, the Company had received $3.9 million of cost reimbursement payments under the Acceleron Collaboration Agreement and $2.0 million associated with the achievement of specified research milestones. As of December 31, 2022, the Company recorded no unbilled accounts receivable related to reimbursable research and development costs under the Acceleron Collaboration Agreement. As of December 31, 2021, the Company recorded unbilled accounts receivable of $0.7 million related to reimbursable research and development costs under the Acceleron Collaboration Agreement for activities performed during the three months ended December 31, 2021. As of December 31, 2022 and 2021, the Company had recorded no accounts receivable under the Acceleron Collaboration Agreement.

MyoKardia Collaboration Agreement

On July 20, 2020, the Company entered into the MyoKardia Collaboration Agreement, pursuant to which the Company granted to MyoKardia an exclusive worldwide license under certain intellectual property rights to research, develop, make, have made, use, have used, sell, have sold, offer for sale, have offered for sale, import, have imported, export, have exported, distribute, have distributed, market, have marketed, promote, have promoted, or otherwise exploit products directed against certain biological targets identified by the Company that are capable of modulating up to a certain number of genes of interest with relevance to certain genetically defined cardiomyopathies.

Pursuant to a mutually agreed research plan, the Company will perform assay screening and related research activities to identify and validate up to a specified number of potential cardiomyopathy gene targets (“Identified Targets”) for further research, development, manufacture and commercialization by MyoKardia. The Company and MyoKardia will work together to determine how best to advance at each stage of the research activities under the research plan and to identify which of the Identified Targets, if any, meet the criteria set forth in the research plan (the “Cardiomyopathy Target Candidates”). Upon completion of the research plan, the parties will work together to prepare a final data package and MyoKardia may designate certain Cardiomyopathy Target Candidates for MyoKardia’s further exploitation under the MyoKardia Collaboration Agreement (the “Cardiomyopathy Targets”). If MyoKardia does not designate any Cardiomyopathy Targets during the designated period, then the MyoKardia Collaboration Agreement will automatically terminate. If MyoKardia designates one or more Cardiomyopathy Targets, then MyoKardia will be obligated to use commercially reasonable efforts to seek regulatory approval for and to commercialize one product directed against an Identified Target in certain specified countries.

During the period in which the Company is performing the research activities pursuant to the research plan (the “Research Term”) and for a specified period beyond the Research Term if MyoKardia designates a Cardiomyopathy Target, the Company may only use the data generated from such research activities for MyoKardia in accordance with the MyoKardia Collaboration Agreement. During the Research Term and for a specified period thereafter, the Company may not research, develop, manufacture, commercialize, use, or otherwise exploit any compound or product (a) that is a Compound or Product under the MyoKardia Collaboration Agreement that is directed against the Cardiomyopathy Target Candidates for the treatment, prophylaxis, or diagnosis of any indication or (b) for the treatment of any genetically defined cardiomyopathies shown to be related to certain specified genes of interest that are modulated by the Cardiomyopathy Targets.

Under the MyoKardia Collaboration Agreement, MyoKardia made a $10.0 million upfront payment and a $2.5 million payment as prepaid research funding to the Company in July 2020. MyoKardia will also reimburse the Company for the costs of the research activities not covered by the prepaid research funding, up to a maximum amount of total research funding (including the prepaid research funding). Upon the achievement of specified preclinical, development and sales milestones, the Company will be entitled to preclinical milestone payments, development milestone payments and sales milestone payments of up to $298.5 million in the aggregate per target for certain Identified Targets, and of up to $150.0 million in the aggregate per target for certain other Identified Targets. To date, the Company has achieved a $2.5 million specified preclinical milestone. MyoKardia will also pay the Company tiered royalties ranging from a mid single-digit percentage to a low double-digit percentage based on MyoKardia’s, and any of its affiliates’ and sublicensees’, annual worldwide net sales of products under the MyoKardia Collaboration Agreement directed against any Identified Target. The royalties are payable on a product-by-product basis during a specified royalty term, and may be reduced in specified circumstances.

The MyoKardia Collaboration Agreement continues on a country-by-country and product-by-product basis until the last to expire royalty term for a product, at which time the MyoKardia Collaboration Agreement expires with respect to such product in such country. Either party has the right to terminate the MyoKardia Collaboration Agreement if the other party has materially breached in the performance of its obligations under the MyoKardia Collaboration Agreement and such breach has not been cured within the applicable cure period. MyoKardia also has the right to terminate the MyoKardia Collaboration Agreement for convenience in its entirety or on a target-by-target, product-by-product or molecule-by-molecule basis.

Accounting Analysis

Identification of the Contract

The Company assessed the MyoKardia Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606.

Identification of the Promises and Performance Obligations

The Company determined that the MyoKardia Collaboration Agreement contains the following promises: (i) an exclusive worldwide license under certain intellectual property rights, including rights to a specified number of potential cardiomyopathy gene targets identified by the Company for further research, development, manufacture and commercialization for the treatment, prophylaxis, or diagnosis of certain genetically defined cardiomyopathies that was conveyed at the inception of the arrangement (the “MyoKardia License”), (ii) research services to identify and validate potential biological targets (the “MyoKardia Research Services”), and (iii) participation in the joint steering committee (the “MyoKardia JSC”).

The Company assessed the above promises and concluded that the MyoKardia License is not capable of being distinct from the MyoKardia Research Services given that the MyoKardia License has limited value without the performance of the MyoKardia Research Services and the MyoKardia Research Services can only be performed by the Company due to their specialized nature. Therefore, the Company has concluded that the MyoKardia License and the MyoKardia Research Services represent a single combined performance obligation.

The Company also assessed the participation on the MyoKardia JSC and concluded that the promise is quantitatively and qualitatively immaterial in the context of the MyoKardia Collaboration Agreement. Accordingly, the Company has disregarded its participation on the MyoKardia JSC as a performance obligation.

Determination of the Transaction Price

The Company received a non-refundable upfront payment of $10.0 million, which the Company included in the transaction price. In December 2021, the Company achieved a $2.5 million specified preclinical milestone associated with the MyoKardia Collaboration Agreement, which was previously constrained due to the significant uncertainty regarding whether such preclinical milestone would be achieved. The Company included this amount in the transaction price as of December 31, 2021. Based on the continued uncertainty associated with the achievement of any of the remaining preclinical and development milestone payments that the Company is eligible to receive, the Company has constrained the variable consideration associated with those milestone payments and excluded them from the transaction price. As part of its evaluation of constraining the preclinical and development milestones, the Company considered numerous factors, including the fact that the achievement of the preclinical and development milestones are contingent upon the results of the underlying preclinical and development activities and are thus outside of the control of the Company.

The Company also included in the transaction price the expected amount of costs to be reimbursed for the MyoKardia Research Services, which includes the $2.5 million prepaid research funding payment that the Company received in the third quarter of 2020.

The Company reassesses the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjusts its estimate of the transaction price. There was no change in the amount of variable consideration constrained during the year ended December 31, 2022.

Any consideration related to sales milestone payments (including royalties) will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to MyoKardia and therefore are recognized at the later of when the related sales occur or the performance obligation is satisfied.

Allocation of the Transaction Price to Performance Obligations

As noted above, the Company has identified a single performance obligation associated with the MyoKardia Collaboration Agreement. Therefore, the Company will allocate the entire amount of the transaction price to the identified single performance obligation.

Recognition of Revenue

The Company recognizes revenue related to the MyoKardia Collaboration Agreement over time as the MyoKardia Research Services are rendered. The Company has concluded that an input method is a representative depiction of the transfer of services under the MyoKardia Collaboration Agreement. The method of measuring progress towards the delivery of the services incorporates actual cumulative internal and external costs incurred relative to total internal and external costs expected to be incurred to satisfy the performance obligation. The period over which total costs are estimated reflects the Company’s estimate of the period over which it will perform the MyoKardia Research Services. Changes in estimates of total internal and external costs expected to be incurred are recognized in the period of change as a cumulative catch-up adjustment.

During the year ended December 31, 2022, the Company recognized $5.3 million of collaboration revenue associated with the MyoKardia Collaboration Agreement, which includes $3.2 million of revenue recognized that was included in deferred revenue as of December 31, 2021. During the year ended December 31, 2021, the Company recognized $9.6 million of collaboration revenue associated with the MyoKardia Collaboration Agreement, which includes $6.7 million of revenue recognized that was included in deferred revenue as of December 31, 2021 and a cumulative catch-up adjustment of $1.7 million attributable to the removal of the constraint associated with the $2.5 million preclinical milestone achieved in December 2021. As of December 31, 2022 and 2021, the Company recorded deferred revenue of $0.9 million and $4.1 million, respectively, associated with the MyoKardia Collaboration Agreement, which is classified as either current or net of current portion in the accompanying consolidated balance sheets based on the period over which the revenue is expected to be recognized. The aggregate deferred revenue balance represents the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of December 31, 2022 and 2021. As of December 31, 2022, the Company had received $5.6 million of cost reimbursement payments under the MyoKardia Collaboration Agreement and $2.5 million associated with the achievement of a preclinical milestone. As of December 31, 2021, the Company had received $3.2 million of cost reimbursement payments under the MyoKardia Collaboration Agreement and no milestone or royalty payments. As of December 31, 2022, the Company recorded unbilled accounts receivable of $0.2 million related to reimbursable research and development costs under the MyoKardia Collaboration Agreement for activities performed during the three months ended December 31, 2022. As of December 31, 2021, the Company recorded unbilled accounts receivable of $0.5 million related to reimbursable research and development costs under the MyoKardia Collaboration Agreement for activities performed during the three months ended December 31, 2021. As of December 31, 2022, the Company recorded no accounts receivable under the MyoKardia Collaboration Agreement. As of December 31, 2021, the Company recorded accounts receivable of $2.5 million under the MyoKardia Collaboration Agreement associated with the achievement of a preclinical milestone in December 2021.

9. Stock-based Compensation Expense

2016 Stock Incentive Plan

In July 2016, the Company adopted the 2016 Stock Incentive Plan (the “2016 Plan”), which provided for the grant of restricted stock awards, restricted stock units, incentive stock options, non-statutory stock options, and other stock-based awards to the Company’s eligible employees, officers, directors, consultants, and advisors. As of the effective date of the 2019 Stock Incentive Plan (the “2019 Plan”), and as of December 31, 2022 and 2021, no shares remained available for future issuance under the 2016 Plan. Any options or other awards outstanding under the 2016 Plan remain outstanding and effective.

2019 Stock Incentive Plan

On July 2, 2019, the Company’s stockholders approved the 2019 Plan, which became effective on July 17, 2019. The 2019 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to the Company’s officers, employees, directors, consultants and advisors. The number of shares initially reserved for issuance under the 2019 Plan was 2,017,142 shares, plus the shares of common stock remaining available for issuance under the 2016 Plan as of July 17, 2019. The number of shares reserved was annually increased on January 1, 2020 and will be increased each January 1 thereafter through January 1, 2029 by the least of (i) 2,000,000 shares, (ii) 4% of the number of shares of the Company’s common stock outstanding on the first day of each such year or (iii) an amount determined by the Company’s board of directors. As of December 31, 2022, there were 1,941,054 shares available for future issuance under the 2019 Plan. On January 1, 2023, the number of shares reserved for issuance under the 2019 Plan was increased by 2,000,000 shares.

The shares of common stock underlying any awards that expire, terminate, or are otherwise surrendered, cancelled, forfeited or repurchased by the Company under the 2016 Plan or the 2019 Plan will be added back to the shares of common stock available for issuance under the 2019 Plan. As of July 17, 2019, no further awards will be made under the 2016 Plan.

2022 Inducement Stock Incentive Plan

In February 2022, the Company's board of directors adopted the 2022 Inducement Stock Incentive Plan (the "Inducement Plan"), pursuant to which the Company may grant, subject to the terms of the Inducement Plan and Nasdaq rules, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, and other stock-based awards. The Company initially reserved a total of 1,750,000 shares of common stock for the issuance of awards under the Inducement Plan. The number of shares reserved and available for issuance under the Inducement Plan can be increased at any time with the approval of the Company’s board of directors. The Inducement Plan permits the board of directors, a delegated committee of the board of directors, or a delegated officer of the Company to grant the stock-based awards available under the Inducement Plan to attract key employees for the growth of the Company. As of December 31, 2022, there were 329,880 shares available for future issuance under the Inducement Plan. Effective March 8, 2023, the Company's board of directors amended the Inducement Plan to increase the number of shares reserved for issuance by 2,000,000 shares.

Restricted Stock Awards

The Company may repurchase unvested restricted stock awards at the original purchase price if employees or non-employees are terminated or cease their employment or service relationship with the Company. Shares of common stock repurchased from employees and non-employees are shares held in the Company’s treasury (“Treasury Shares”). The board of directors may, at its discretion, authorize that the Treasury Shares be returned to the pool of authorized but unissued common stock.

The shares of common stock underlying restricted stock awards typically vest over a four-year period. The shares of common stock are recorded in stockholders’ equity as they vest.

Stock Options

Stock options granted by the Company typically vest over a four year period and have a ten year contractual term. Shares issued upon the exercise of stock options are issued from the Company’s pool of authorized but unissued common stock. In addition to stock options granted under the 2019 Plan and 2016 Plan, the Company has granted stock options as material inducements to employment in accordance with Nasdaq Listing Rule 5635(c)(4), which were granted outside of the 2019 Plan and 2016 Plan. The following table summarizes the Company’s stock option activity during the year ended December 31, 2022:

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock as of the balance sheet date for those options that had exercise prices lower than the fair value of the Company’s common stock.

The weighted average grant date fair value of stock options granted in the years ended December 31, 2022 and 2021 was $7.62 per share and $11.37 per share, respectively. The total intrinsic value of stock options exercised in the years ended December 31, 2022 and 2021 was $2.6 million and $3.5 million, respectively.

Restricted Stock Units

The Company has also granted restricted stock units. The shares of common stock underlying restricted stock units typically vest over a four-year period. The shares of common stock are recorded in stockholders’ equity as they vest.

The aggregate intrinsic value of all restricted stock units and restricted stock awards that vested during the years ended December 31, 2022 and 2021 was $0.2 million and $1.5 million, respectively.

Stock-based Compensation Expense

As of December 31, 2022, the Company had an aggregate of $32.0 million of unrecognized stock-based compensation expense, which is expected to be recognized over a weighted average period of 2.86 years.

2019 Employee Stock Purchase Plan

On July 2, 2019, the Company’s stockholders approved the 2019 Employee Stock Purchase Plan (the “ESPP”), which became effective on July 17, 2019. A total of 252,142 shares of common stock were initially reserved for issuance under the ESPP. In addition, the number of shares of common stock reserved under the ESPP was annually increased on January 1, 2020, and will be increased on each January 1 thereafter through January 1, 2029, by the least of (i) 428,571 shares of common stock, (ii) 1% of the number of shares of the Company’s common stock outstanding on the first day of each such year or (iii) an amount determined by the Company’s board of directors. As of December 31, 2022, there were 1,061,279 shares available for future issuance under the ESPP. On January 1, 2023, the number of shares reserved for issuance under the 2019 ESPP was increased by 428,571 shares.

Property and equipment, net consisted of the following (in thousands):

17. Net Loss per Share