Subsequent events - Additional Information (Details)	Jan. 05, 2022
Subsequent Event
Subsequent Event [Line Items]
Description of clinical trial Agreement	BioAtla and Bristol-Myers Squibb Company (“BMS”) entered into a clinical trial collaboration and supply agreement (the “BMS Agreement”). Under the terms of the BMS Agreement, BioAtla and BMS will collaborate on clinical trials of separate combination therapies using two of BioAtla’s Conditionally Active Biologic Antibody Drug Conjugates, BA3011 and BA3021, each in combination with Opdivo® (nivolumab), BMS’ proprietary anti-PD-1 monoclonal antibody product. The Company will serve as the study sponsor of the scheduled studies and will be responsible for costs associated with the trial execution. BMS will provide Opdivo® clinical drug supply at no cost for the combination study trials. After the completion of the combination therapy trials, the Company is obligated to provide BMS with a final report of the data resulting from the trial. There was no impact to the Company's financial results for the year ended December 31, 2021 as a result of this agreement.