Pyxis Oncology Releases Preliminary Data from MICVO Clinical Trials

Pyxis Oncology announced preliminary data from its ongoing Phase 1 clinical studies evaluating micvotabart pelidotin, a first-in-concept antibody-drug conjugate targeting extradomain-B of fibronectin, a non-cellular structural component of the tumor extracellular matrix, in patients with recurrent/metastatic head and neck squamous cell carcinoma. The update includes preliminary data from both the Phase 1 monotherapy study in 2L+ R/M HNSCC and the Phase 1/2 study evaluating MICVO in combination with Merck's anti-PD-1 therapy, pembrolizumab, in 1L/2L+ R/M HNSCC. The cutoff for all data reported below is as of November 3, 2025. Key findings are as follows: Monotherapy: The ongoing MICVO Phase 1 monotherapy study is a two-part study. Part 1 was a dose escalation study across multiple doses and tumor types, with initial data shared in November 2024. Part 2, a dose expansion cohort at 5.4 mg/kg in 2L+ R/M HNSCC, is currently ongoing. The data below incorporate all R/M HNSCC patients dosed at 5.4 mg/kg in the MICVO Phase 1 monotherapy study. 18 patients were treated at 5.4 mg/kg; intravenous dosed every three weeks; 13 patients were evaluable for response; All patients treated had prior systemic therapy, including: Median of 3 prior lines of therapy; 100% had prior platinum-based therapy; 100% had prior checkpoint inhibitor therapy; 67% had prior taxane therapy; 50% had prior EGFR targeting therapy; Confirmed overall response rate of 46%, including 1 complete response by RECIST v1.1. Confirmed responses observed in both arms of dose expansion: post platinum & anti-PD(L)-1 experienced patients and post EGFRi and/or anti-PD(L)-1 experienced patients Arm 1: 60% confirmed ORR; Arm 2: 25% confirmed ORR; Confirmed responses observed in patients with HPV-positive, HPV-negative, and HPV-not applicable tumors; Disease control rate of 92%; 12 patients demonstrated significant tumor regression or tumor control 1 patient with progressive disease had a verrucous subtype of HNSCC, which is often resistant to chemotherapy and typically managed surgically; MICVO was generally well tolerated, with no Grade 4 ADC payload treatment-related adverse events of interest observed. No Grade 5 events occurred. TRAEs were observed in 89% of patients Grade greater than or equal to3 TRAEs occurred in 56% of patients. TRAEs leading to treatment discontinuation were observed in 28% of patients. 100% of patients who had TRAEs leading to treatment discontinuation had "high bodyweight"; Adjusted Ideal Bodyweight dosing, which has demonstrated improved tolerability without sacrificing activity in clinical studies of other ADCs, is planned to be implemented in ongoing and future clinical studies. Combination Therapy: The ongoing MICVO Phase 1/2 study evaluating MICVO in combination with KEYTRUDA is part of a Clinical Trial Collaboration Agreement with Merck and is currently in dose escalation across multiple doses and tumor types, including 1L/2L+ R/M HNSCC. The data below incorporate all R/M HNSCC patients dosed in the MICVO Phase 1/2 combination study at 3.6 mg/kg and 4.4 mg/kg. 7 patients were treated in total, 4 at 3.6 mg/kg and 3 at 4.4 mg/kg of MICVO, plus fixed dose 200 mg of pembrolizumab; IV Q3W. All patients were evaluable for response. All patients treated to date were HPV-positive. Enrollment of HPV-negative and HPV-not applicable patients is anticipated as additional global clinical trial sites are activated. All patients treated had prior systemic therapy, including: N=4, 1L HNSCC, median of 1 prior therapy; 100% had prior platinum-based therapy administered with radiation in the adjuvant or definitive setting; 25% had prior taxane administered in the neoadjuvant setting; N=3, 2L+ HNSCC, median of 3 prior lines of therapy; 100% had prior platinum-based therapy; 100% had prior checkpoint inhibitor therapy; 33% had prior taxane therapy; Confirmed overall response rate of 71%; Responses occurred across a range of PD(L)-1 CPS scores; Responses were observed in patients who received and had disease progression following prior checkpoint inhibitor treatment; DCR of 100%; All 7 patients demonstrated significant tumor regression. MICVO was generally well tolerated, with no Grade 3 or Grade 4 ADC payload TRAEs of interest observed. No Grade 5 events occurred.TRAEs were observed in 86% of patients; There were no TRAEs leading to treatment discontinuation; Lack of overlapping toxicities between MICVO and KEYTRUDA observed to date.