Vaccinex (VCNX) Reports Two Complete Responses in First Three Patients Enrolled in the Phase 1b/2 KEYNOTE-B84 Study of Pepinemab in Combination with KEYTRUDA (pembrolizumab) in Patients with Recurrent

January 26, 2022 8:03 AM EST
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Vaccinex, Inc. (Nasdaq: VCNX, Vaccinex, the Company), a clinical-stage biotechnology company pioneering a differentiated approach to treating cancer and neurodegenerative disease through the inhibition of semaphorin 4D (SEMA4D), today reported positive interim response data in the Phase Ib segment of the KEYNOTE-B84 study of Vaccinex’s pepinemab in combination with Merck’s (known as MSD outside of the United States and Canada) anti-PD-1 therapy KEYTRUDA (pembrolizumab) in patients with recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC).

Among the three patients enrolled in the Phase1b safety segment of the study, two patients have been observed to experience a complete response (CR), as per RECIST v.1.1. Biomarker analysis revealed that tumors in both responders expressed low levels of PD-L1 biomarker (CPS<20), a subset of HNSCC patients who have historically low response rates to anti-PD-1/L1 antibodies administered as single agents.

KEYNOTE-B84 Study (NCT04815720)

The Phase 1b safety observation segment of KEYNOTE-B84 enrolled 3 patients to assess potential Dose Limiting Toxicity (DLT) for pepinemab, Vaccinex’s monoclonal antibody inhibitor of SEMA4D, in combination with KEYTRUDA (pembrolizumab), Merck’s anti-PD-1 therapy (pembrolizumab), in R/M HNSCC. The trial’s Data Safety Monitoring Boarddetermined that the recommended phase 2 dose of pepinemab (20 mg/kg Q3W), in combination with KEYTRUDA (200 mg Q3W), appeared to be well-tolerated. Treatment was continued following the 28-day Safety Observation Period, and, as per protocol, an on-treatment biopsy of a target lesion was obtained at week 5, and scans for tumor response assessments were performed week 9 and every 6-weeks thereafter. Two of these initial three patients have been observed to experience a complete response (CR), as per RECIST v.1.1.

Case Study: #1, Complete Response (Confirmed)

  • Oropharyngeal cancer
  • Adverse Events: none of notable severity
  • Target lesions: metastatic lung lesions (Left 11mm, Right 15mm)
    • Biopsy at Week 5: left lung target lesion: “no evidence of malignancy. Fibrous and chronic inflammation”
    • Week 9 scan: Stable Disease, 19% decrease in target lesion size
    • Week 15 scan: Complete Response, 100% decrease
    • Week 21 scan: Confirmed, Complete Response
  • Biomarkers: PD-L1: Combined Positive Score (CPS) <20 and HPV status: negative

Case Study: #2. Complete Response (pending confirmation by repeat scan)

  • Larynx cancer with direct invasion into thyroid and neck
  • Adverse Events: Grade 1 rash
  • Target lesion: neck mass (37mm)
    • Biopsy at Week 5: no evidence of malignancy”
    • Week 9 scan: Complete Response, 100% decrease
    • Week 15 scan: Confirmation pending, expected early March 2022
  • Biomarkers: PD-L1: CPS <1 and HPV status: negative

The third patient in this group who had cancer of the tongue was deemed by investigator to have clinical progression and withdrew from the study at Week 6, which was prior to the first radiologic tumor response assessment at Week 9, and was, therefore, non-evaluable for tumor response. Patient also suffered serious adverse events (SAE) including dehydration and hyperglycemia that were attributed to a pre-existing co-morbidity (diabetes and other complications) unrelated to treatment.

Maurice Zauderer, Ph.D., President and Chief Executive Officer of Vaccinex, remarked, “We believe there is a strong rationale for continued development of pepinemab in combination with KEYTRUDA in HNSCC because these tumors are known to express high levels of SEMA4D and preclinical studies by Vaccinex and others have indicated that SEMA4D induces increased numbers and activity of myeloid suppressor cells that inhibit immune responses. Notably, pepinemab in combination with KEYTRUDA does not include administration of chemotherapy. The KEYNOTE-B84 study is accruing patients in the now open expansion phase which will enroll up to an additional 62 patients in approximately equal groups of patients with CPS <20 and CPS ≥20 across 18 U.S. trial sites. We look forward to sharing further results at a medical conference as the study progresses, with interim analysis around the midpoint of enrollment (2H 2022).”

Vaccinex has global commercial and development rights to pepinemab, and is sponsor of the KEYNOTE-B84 study which is being performed in collaboration with Merck Sharp & Dohme Corp, a subsidiary of Merck and Co, Inc. Kenilworth, NJ, USA. Additional information about the study is available at: link.

KEYTRUDA is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co. Inc., Kenilworth, NJ, USA.

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