Collaboration Agreements	3 Months Ended
Mar. 31, 2023
Collaboration Agreement [Abstract]
Collaboration Agreements	Note 8 - Collaboration Agreements BeiGene Agreement In July 2020, the Company and BeiGene, Ltd. (BeiGene) entered into a Collaboration Agreement (the BeiGene Agreement) to develop and commercialize the Company’s novel core inhibitor product candidates vebicorvir (VBR), ABI-H2158 and ABI-H3733 (the Licensed Product Candidates) for chronic HBV infection in the People’s Republic of China, Hong Kong, Taiwan and Macau. As of March 31, 2023, the only remaining performance obligation under the BeiGene Agreement not considered to be complete is the transfer of the ABI-H3733 License. The transaction price allocated to ABI-H3733 of $2.7 million was recognized as a long-term deferred revenue contract liability as of March 31, 2023 and December 31, 2022, and will be recognized as revenue when the Company provides pre-Phase 3 clinical study know-how and development results for ABI-H3733 to BeiGene or a termination of the BeiGene Agreement for ABI-H3733. During the three months ended March 31, 2023 and 2022, the Company did not recognize any revenue or increase or reduction of research and development expense under the BeiGene Agreement. The Company incurred $3.5 million in incremental costs of obtaining the BeiGene Agreement in 2020. These contract costs have been capitalized and are being recognized consistent with the pattern of recognition of revenue associated with the Licensed Product Candidates. As of March 31, 2023 and December 31, 2022, the remaining unamortized contract costs are $0.2 million and are included in other assets on the condensed consolidated balance sheet. Arbutus Biopharma Agreement In August 2020, the Company and Arbutus Biopharma Corporation (Arbutus Biopharma) entered into a Clinical Trial Collaboration Agreement (the Arbutus Biopharma Agreement) to conduct a randomized, multi-center, open-label Phase 2 clinical trial to explore the safety, pharmacokinetics and antiviral activity of the triple combination of VBR, AB-729 and a nucleos(t)ide analog reverse transcriptase inhibitor (NrtI) compared to the double combinations of VBR with a NrtI and AB-729 with a NrtI. Under the Arbutus Biopharma Agreement, Assembly and Arbutus Biopharma share responsibility for the costs of the trial equally, excluding manufacturing supply which are the burden of each company to supply their respective drugs, VBR and AB-729. Assembly is responsible for conducting this clinical trial with Arbutus Biopharma reimbursing Assembly its share of expenses. In February 2023, Assembly and Arbutus Biopharma decided to terminate the Phase 2 clinical trial early, at the end of the 48-week on-treatment period, and are in the process of closing the study. Reimbursements and cost-sharing portions from Arbutus Biopharma are reflected as a reduction of research and development expense when realized in the Company’s condensed consolidated statements of operations. During both the three months ended March 31, 2023 and 2022, the Company recognized a reduction of research and development expenses of $0.6 million under the Arbutus Biopharma Agreement.

Collaboration Agreements

3 Months Ended

Mar. 31, 2023

Note 8 - Collaboration Agreements

BeiGene Agreement

In July 2020, the Company and BeiGene, Ltd. (BeiGene) entered into a Collaboration Agreement (the BeiGene Agreement) to develop and commercialize the Company’s novel core inhibitor product candidates vebicorvir (VBR), ABI-H2158 and ABI-H3733 (the Licensed Product Candidates) for chronic HBV infection in the People’s Republic of China, Hong Kong, Taiwan and Macau.

As of March 31, 2023, the only remaining performance obligation under the BeiGene Agreement not considered to be complete is the transfer of the ABI-H3733 License. The transaction price allocated to ABI-H3733 of $2.7 million was recognized as a long-term deferred revenue contract liability as of March 31, 2023 and December 31, 2022, and will be recognized as revenue when the Company provides pre-Phase 3 clinical study know-how and development results for ABI-H3733 to BeiGene or a termination of the BeiGene Agreement for ABI-H3733. During the three months ended March 31, 2023 and 2022, the Company did not recognize any revenue or increase or reduction of research and development expense under the BeiGene Agreement.

The Company incurred $3.5 million in incremental costs of obtaining the BeiGene Agreement in 2020. These contract costs have been capitalized and are being recognized consistent with the pattern of recognition of revenue associated with the Licensed Product Candidates. As of March 31, 2023 and December 31, 2022, the remaining unamortized contract costs are $0.2 million and are included in other assets on the condensed consolidated balance sheet.

Arbutus Biopharma Agreement

In August 2020, the Company and Arbutus Biopharma Corporation (Arbutus Biopharma) entered into a Clinical Trial Collaboration Agreement (the Arbutus Biopharma Agreement) to conduct a randomized, multi-center, open-label Phase 2 clinical trial to explore the safety, pharmacokinetics and antiviral activity of the triple combination of VBR, AB-729 and a nucleos(t)ide analog reverse transcriptase inhibitor (NrtI) compared to the double combinations of VBR with a NrtI and AB-729 with a NrtI. Under the Arbutus Biopharma Agreement, Assembly and Arbutus Biopharma share responsibility for the costs of the trial equally, excluding manufacturing supply which are the burden of each company to supply their respective drugs, VBR and AB-729. Assembly is responsible for conducting this clinical trial with Arbutus Biopharma reimbursing Assembly its share of expenses. In February 2023, Assembly and Arbutus Biopharma decided to terminate the Phase 2 clinical trial early, at the end of the 48-week on-treatment period, and are in the process of closing the study.

Reimbursements and cost-sharing portions from Arbutus Biopharma are reflected as a reduction of research and development expense when realized in the Company’s condensed consolidated statements of operations. During both the three months ended March 31, 2023 and 2022, the Company recognized a reduction of research and development expenses of $0.6 million under the Arbutus Biopharma Agreement.