CX-072 (pacmilimab), a Probody PD-L1 inhibitor, in combination with ipilimumab in patients with advanced solid tumors (PROCLAIM-CX-072): a first-in-human, dose-finding study.

Abstract

BACKGROUND:

Probody® therapeutics are antibody prodrugs designed to be activated by tumor-associated proteases. This conditional activation restricts antibody binding to the tumor microenvironment, thereby minimizing 'off-tumor' toxicity. Here, we report the phase 1 data from the first-in-human study of CX-072 (pacmilimab), a Probody immune checkpoint inhibitor directed against programmed death-ligand 1 (PD-L1), in combination with the anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) antibody ipilimumab.

METHODS:

Adults (n=27) with advanced solid tumors (naive to PD-L1/programmed cell death protein 1 or CTLA-4 inhibitors) were enrolled in the phase 1 combination therapy dose-escalation portion of this multicenter, open-label, phase 1/2 study (NCT03013491). Dose-escalation pacmilimab/ipilimumab followed a standard 3+3 design and continued until the maximum tolerated dose (MTD) was determined. Pacmilimab+ipilimumab was administered intravenously every 3 weeks for four cycles, followed by pacmilimab administered every 2 weeks as monotherapy. The primary objective was identification of dose-limiting toxicities and determination of the MTD. Other endpoints included the rate of objective response (Response Evaluation Criteria In Solid Tumors v.1.1).

RESULTS:

Twenty-seven patients were enrolled in pacmilimab (mg/kg)+ipilimumab (mg/kg) dose-escalation cohorts: 0.3+3 (n=6); 1+3 (n=3); 3+3 (n=3); 10+3 (n=8); 10+6 (n=6); and 10+10 (n=1). Dose-limiting toxicities occurred in three patients, one at the 0.3+3 dose level (grade 3 dyspnea/pneumonitis) and two at the 10+6 dose level (grade 3 colitis, grade 3 increased aspartate aminotransferase). The MTD and recommended phase 2 dose was pacmilimab 10 mg/kg+ipilimumab 3 mg/kg administered every 3 weeks. Pacmilimab-related grade 3-4 adverse events (AEs) and grade 3-4 immune-related AEs were reported in nine (33%) and six (22%) patients, respectively. Three patients (11%) discontinued treatment because of AEs. The overall response rate was 19% (95% CI 6.3 to 38.1), with one complete (anal squamous cell carcinoma) and four partial responses (cancer of unknown primary, leiomyosarcoma, mesothelioma, testicular cancer). Responses lasted for >12 months in four patients.

CONCLUSIONS:

The MTD and recommended phase 2 dose of pacmilimab (10 mg/kg)+ipilimumab (3 mg/kg) every 3 weeks is active and has a favorable tolerability profile.

• Authors: Rachel E Sanborn, Omid Hamid, Elisabeth Ge de Vries, Patrick A Ott, Javier Garcia-Corbacho, Valentina Boni, Johanna Bendell, Karen A Autio, Daniel C Cho, Ruth Plummer, Mark Stroh, Lawrence Lu, Fiona Thistlethwaite
• Journal: Journal for immunotherapy of cancer (J Immunother Cancer) Vol. 9 Issue 7 (07 2021) ISSN: 2051-1426 [Electronic] England
• PMID: 34301808 (Publication Type: Clinical Trial, Phase I, Clinical Trial, Phase II, Journal Article, Multicenter Study, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Chemical References

• Antibodies, Monoclonal
• B7-H1 Antigen
• CD274 protein, human
• Immune Checkpoint Inhibitors
• Ipilimumab
• Prodrugs

Topics

• Adult
• Aged
• Antibodies, Monoclonal (administration & dosage)
• Antineoplastic Combined Chemotherapy Protocols (therapeutic use)
• B7-H1 Antigen (antagonists & inhibitors, immunology)
• Dose-Response Relationship, Drug
• Female
• Humans
• Immune Checkpoint Inhibitors (administration & dosage)
• Immunotherapy
• Ipilimumab (administration & dosage)
• Male
• Middle Aged
• Neoplasms (drug therapy, immunology)
• Prodrugs (administration & dosage)