Shares of Pyxis Oncology (NASDAQ:PYXS) declined 7% on Tuesday after the company released updated results from its Phase 1 monotherapy trial of Micvotabart Pelidotin (MICVO) in patients with second-line and beyond recurrent/metastatic head and neck squamous cell carcinoma.
The dataset, focused on patients dosed at 5.4 mg/kg administered intravenously once every three weeks, included 33 efficacy-evaluable participants. Among those patients, the trial recorded a confirmed objective response rate of 36% and a disease control rate of 94%. Median progression-free survival for the group was 6.2 months. The probability of survival at 12 months was reported as 79%, while median overall survival has not yet been reached.
Investigators observed clinical activity across key subgroups, including stratification by HPV status and by prior treatment history. Response rates differed by prior exposure to epidermal growth factor receptor (EGFR) inhibitors: patients with prior EGFR inhibitor treatment had a confirmed objective response rate of 28%, compared with a 47% response rate in those without prior EGFR inhibitor therapy.
On safety, the company said no new safety signals were identified. Reported treatment-related adverse events were described as consistent with patterns seen for other antibody-drug conjugates that use auristatin payloads. In the safety-evaluable population of 35 patients, 54.3% experienced treatment-related adverse events of Grade 3 or higher. Treatment discontinuation due to adverse events occurred in 14.3% of patients. No treatment-related deaths were reported.
Looking ahead, Pyxis intends to start a pivotal Phase 3 trial, named Headliner, in mid-2027. That move follows an End of Phase 2 meeting with the U.S. Food and Drug Administration that the company expects to occur in the first quarter of 2027. The randomized Headliner trial is planned to enroll roughly 500 patients with second- or third-line recurrent/metastatic head and neck squamous cell carcinoma, and will compare MICVO against investigators' choice of cetuximab, docetaxel, or methotrexate.
MICVO is an antibody-drug conjugate designed to target extradomain-B of fibronectin, a structural element of the tumor extracellular matrix. The program's early efficacy and the safety profile reported in this cohort form the basis for the planned pivotal study.
Context and market reaction
Despite the positive efficacy and safety readouts described above, Pyxis Oncology's stock declined on the day the update was published. The company will move toward a randomized Phase 3 study contingent on the planned FDA interaction in early 2027 and subsequent trial initiation in mid-2027.
Conclusion
The Phase 1 results for MICVO demonstrate measurable activity in a heavily pretreated head and neck cancer population and a safety profile consistent with other auristatin-based antibody-drug conjugates. Pyxis has outlined a clear path to a pivotal trial, while investors reacted with a one-day share price decline.