SNSE Clinical Data Surpasses Historical Benchmarks in PD-(L)1 Resistant Tumors
Sensei Biotherapeutics (NASDAQ:SNSE) has delivered new hope for patients with PD-(L)1 resistant tumors, announcing that its lead candidate, solnerstotug, achieved a 50% six-month progression-free survival (PFS) rate at the higher 15 mg/kg dose in its ongoing Phase 1/2 trial. This rate markedly outpaces historical outcomes for this treatment-refractory group and stands out at the 2025 ESMO Congress.
Dose-Dependent Efficacy Stands Out: 50% Six-Month PFS at 15 mg/kg
The clinical study enrolled 44 patients with immunotherapy-responsive (“hot”) tumors and 20 with “cold” tumors. Among the 41 patients with prior PD-(L)1 treatment who had developed resistance, solnerstotug in combination with cemiplimab (Regeneron’s PD-1 inhibitor) produced noteworthy results at the 15 mg/kg dose:
| Dose Group | Six-Month PFS (%) | Clinical Responses (n) |
|---|---|---|
| 15 mg/kg + cemiplimab | 50 | 6 (all responses in PD-(L)1 resistant patients at this dose) |
| 3 mg/kg + cemiplimab | 24 | 0 |
| Historical Benchmarks (docetaxel 2L NSCLC) | 10-20 | — |
To put these numbers in perspective, docetaxel—the current second-line standard for PD-(L)1 resistant non-small cell lung cancer—delivers only a 10-20% six-month PFS, and rechallenging with immunotherapy after resistance yields benefits for less than 5% of patients.
Durable Responses with Unique Delayed Onset
Beyond higher response rates, solnerstotug demonstrated a striking pattern: four out of six responders experienced durable disease control, often followed by a delayed but lasting response between 18 and 54 weeks—well beyond the typical 2-3 month time-to-response seen with standard immunotherapies. Highlighted outcomes include:
- Merkel Cell Carcinoma patient: complete response at week 18, with ongoing benefit beyond 54 weeks
- Microsatellite Instability-High Colorectal Cancer patient: partial response at week 36, lasting over 33 weeks
- Non-Small Cell Lung Cancer (NSCLC) patient: partial response at week 54
This pattern suggests a potentially novel mechanism of action—one that may enable tumor re-sensitization even after prior immune checkpoint inhibitor failure.
Safety Profile Remains Favorable and Consistent
Solnerstotug continued to show manageable safety, with only six cases of mild (grade 1) cytokine release syndrome (CRS), all at the 15 mg/kg dose, and no new safety signals identified. No objective responses were observed in “cold” tumors or in the 3 mg/kg cohort, indicating a dose-response relationship in “hot” tumor types.
| Adverse Event | Frequency (All Patients) |
|---|---|
| Grade 1 Cytokine Release Syndrome | 6 (all manageable, 15 mg/kg dose) |
| New Safety Signals | None reported |
Phase 2 Studies in the Pipeline: Focus on Unmet Needs
Based on these encouraging results, Sensei is moving forward with two Phase 2 trials scheduled for 2026 (pending regulatory feedback and financing): a randomized study in second-line NSCLC after PD-(L)1 inhibitor failure, and a single-arm study in Merkel Cell Carcinoma—where current options are especially limited. Notably, the NSCLC trial will directly compare solnerstotug plus PD-(L)1 inhibitor versus chemotherapy.
Key Takeaway: Solnerstotug Sets a New Bar for PD-(L)1 Resistant Cancer
With a 50% six-month PFS at a higher dose, a durable safety profile, and unique delayed response dynamics, solnerstotug could shift expectations for a group of cancer patients with limited hope from existing therapies. Investors and researchers will be closely watching Sensei’s next steps, including the upcoming October 20 investor webcast and anticipated Phase 2 trial launches.
For more details, visit Sensei Biotherapeutics' investor relations site or attend the webcast on October 20 at 8:00 AM ET.
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