By Elias Schisgall

Shares of Pyxis Oncology dropped after the pharmaceutical company said data from its trials on a treatment for a form of head and neck cancer showed a high incidence of adverse effects.

The stock fell 45%, to $1.85, late Thursday morning, but has risen 19% this year.

The company said Thursday that it saw positive preliminary efficacy data for a Phase 1 trial for micvotabart pelidotin for recurrent/metastatic head and neck squamous cell carcinoma, or R/M HNSCC, along with a Phase 1/2 trial for the treatment in combination with Merck & Co.'s Keytruda for R/M HNSCC patients.

The monotherapy trial suggested a confirmed overall-response rate of 46% and a disease-control rate of 93%. In combination with Keytruda, the confirmed overall-response rate was 71% and the disease-control rate was 100%, according to Pyxis.

Both studies suggested a rate of treatment-related adverse events above 80%, the company said. The adverse events were observed in 89% of patients in the monotherapy trial, with adverse events at or above Grade 3 level--referring to effects that are severe or medically significant but not life threatening--occurring in 56% of patients.

In the combination study, adverse events were observed in 86% of the patients, the Boston company said.

"The preliminary data for MICVO as monotherapy and in combination with pembrolizumab add to the growing body of evidence supporting MICVO's therapeutic potential and highlight its agility as a novel potential treatment option across the recurrent/metastatic head and neck squamous cell carcinoma landscape," Chief Executive Officer Lara Sullivan said Thursday.

The company said it expects to present updated data from the monotherapy study in mid-2026 and data from the combined therapy study in the second half of the year.

Write to Elias Schisgall at elias.schisgall@wsj.com

(END) Dow Jones Newswires

December 18, 2025 11:55 ET (16:55 GMT)

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