Traws Pharma shares fall -22.38% premarket after FDA places tivoxavir on clinical hold due to mutagenicity concerns.

Traws Pharma (TRAW) fell 22.38% in premarket trading after the FDA placed its influenza drug tivoxavir marboxil on clinical hold due to mutagenicity concerns. The agency notified the company of its concerns with the mutagenicity data package for tivoxavir marboxil, a candidate for seasonal and avian influenza, and plans to outline mitigation steps by March 16, 2026. This regulatory setback overshadowed positive Phase 2 results for ratutrelvir, which demonstrated superior tolerability and efficacy compared to PAXLOVID in mild-to-moderate COVID-19 patients. While ratutrelvir’s clinical data were favorable, the FDA’s clinical hold on tivoxavir marboxil—critical for the company’s antiviral portfolio—triggered investor pessimism about regulatory hurdles and delayed development timelines.