sasanlimab

Overview

Sasanlimab (PF-06801591; RN-888; WHO 11161) is a humanized IgG4 monoclonal antibody targeting programmed death-1 (PD‑1). It is being developed as a subcutaneous (SC) checkpoint inhibitor dosed most commonly at 300 mg every 4 weeks. Preclinical work showed selective, high-affinity PD‑1 binding, blockade of PD‑L1/PD‑L2, and T‑cell activation without detectable Fc‑mediated effector function. Clinical development includes a pivotal phase 3 trial in BCG‑naïve, high‑risk non–muscle invasive bladder cancer (NMIBC) and early‑phase studies across solid tumors. (pubmed.ncbi.nlm.nih.gov)

Mechanism of action

• Binds PD‑1 on activated immune cells and blocks PD‑L1/PD‑L2 interactions, relieving inhibitory signaling and enhancing antitumor T‑cell responses; engineered as IgG4 with minimal Fc effector function. (pubmed.ncbi.nlm.nih.gov)
• Translational analyses from a first‑in‑human study found that higher baseline tumor mutational burden (TMB), PD‑L1, CD8, and interferon‑γ–related signatures were associated with better tumor shrinkage on sasanlimab across tumor types and IV/SC routes. (pubmed.ncbi.nlm.nih.gov)

Efficacy

Non–muscle invasive bladder cancer (BCG‑naïve, high‑risk; Phase 3 CREST, NCT04165317) - Randomized 1:1:1: sasanlimab+BCG induction+maintenance (Arm A; n=352) vs sasanlimab+BCG induction only (Arm B; n=352) vs BCG induction+maintenance (Arm C; n=351). Primary endpoint met: event‑free survival (EFS) improved for Arm A vs Arm C (HR 0.68; 95% CI 0.49–0.94; one‑sided p=0.0095). Estimated 36‑month EFS: 82.1% (Arm A) vs 74.8% (Arm C). Benefit was consistent in CIS and T1 subgroups. (pubmed.ncbi.nlm.nih.gov)
- Key secondary comparison (Arm B vs Arm C) was negative (HR 1.16; p=0.312), underscoring the role of BCG maintenance in the combination. In patients with CIS at randomization, complete response (CR) at any time was 89.8% with sasanlimab+BCG induction+maintenance vs 85.2% with BCG alone; 36‑month CR maintenance among responders was 91.7% vs 67.7%, respectively. Median OS not different at interim analysis (~41‑month follow‑up); study ongoing. (pfizer.com)

Advanced solid tumors (Phase Ib/II; SC 300 mg Q4W) - Dose‑expansion cohorts showed confirmed objective response rates (ORR): 16.4% in NSCLC (n=68) and 18.4% in urothelial carcinoma (n=38). Median PFS was 3.7 months (NSCLC) and 2.9 months (urothelial); median OS 14.7 and 10.9 months, respectively. Responses and survival tended to be higher with elevated PD‑L1 and high TMB. (pmc.ncbi.nlm.nih.gov)

Alternative SC dosing (Phase Ib/II) - A randomized pharmacokinetic study in advanced NSCLC/other malignancies evaluated 300 mg Q4W vs 600 mg Q6W SC dosing; it characterized exposure targets and supported SC schedules for further study. (pmc.ncbi.nlm.nih.gov)

Safety

• In phase Ib/II expansion (SC 300 mg Q4W), grade ≥3 treatment‑related adverse events (TRAEs) occurred in 13.2% of patients; overall tolerability was described as favorable. (pmc.ncbi.nlm.nih.gov)
• In the phase 3 CREST trial, the safety profile of sasanlimab+BCG was reported as consistent with known PD‑1 inhibitor class effects; no new safety signals were highlighted in topline disclosures. (reuters.com)

Further reading

• Preclinical characterization of sasanlimab (mechanism/engineering): Al‑Khami et al., Mol Cancer Ther 2020. (aacrjournals.org)
• Biomarker analyses across tumor types and routes (first‑in‑human): Salgado et al., 2021. (pubmed.ncbi.nlm.nih.gov)
• Phase Ib/II SC sasanlimab in NSCLC and urothelial carcinoma (efficacy/safety): Cho et al., ESMO Open 2023. (pmc.ncbi.nlm.nih.gov)
• Alternative SC dosing PK/safety: Penkov et al., Ther Adv Med Oncol 2024 (open access). (pmc.ncbi.nlm.nih.gov)
• Phase 3 CREST primary results in BCG‑naïve, high‑risk NMIBC: PubMed record and company summary. (pubmed.ncbi.nlm.nih.gov)
• Company development page (mechanism, administration, development status, updated Aug 5, 2025). (pfizeroncologydevelopment.com)

Last updated: Oct 2025