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Invikafusp alfa led to tumor regression in target lesions in 52% of patients with tumor mutational burden–high (TMB-H) or microsatellite instability–high (MSI-H) solid tumors resistant to immune checkpoint blockade, according to data from the phase 2 START-001 trial (NCT05592626) presented at the 2025 ESMO Congress.¹

Across the 4 biomarker-enriched populations with TMB-H tumors, TMB-H gastrointestinal cancers, TMB-H metastatic colorectal cancer (mCRC), and MSI-H tumors, the objective response rates (ORRs) were 20.5% (n = 9 of 44), 27.8% (n = 5 of 18), 33.3% (n = 3 of 9), and 30% (n = 3 of 10), respectively. The respective disease control rates were 79.5% (n = 35 of 44), 77.8% (n = 14 of 18), 66.7% (n = 6 of 9), and 70% (n = 7 of 10). Notably, the TMB-H cohort included patients with CRC, gastric, lung, breast, and other cancers.

“Invikafusp alfa, a first-in-class bispecific dual T-cell agonist, demonstrated clinically meaningful monotherapy activity in heavily pretreated immune checkpoint blockade–resistant/insensitive tumors harboring high tumor mutations,” presenting study author Antoine Italiano, MD, PhD, professor of medicine, head of Early Phase Trials Unit at the Institut Bergonié, and head of Precision Medicine at Gustave Roussy in France, stated in the presentation.

What Was the Study Rationale?

Immunotherapy resistance poses a clinical challenge as it limits the number of effective treatment options that are available to patients. Tumor-infiltrating lymphocyte therapies have shown promise in the immuno-oncology (IO)–refractory setting, with Vβ6/10 T-cell subsets representing the most common subset.

Invikafusp alfa was designed to selectively activate and expand Vβ10 T-cell subsets to overcome resistance to immune checkpoint blockade.

What Were the Enrollment Criteria?

Eligibility criteria required that patients have unresectable, locally advanced or metastatic, TMB-H, MSI-H, or virally-associated solid tumors in phase 1, and TMB-H, MSI-H/mismatch repair–deficient (dMMR) tumors, including TMB-H and/or MSI-H CRC in phase 2.² An ECOG performance status of 0 or 1 was required in both phases. Prior treatment with PD-(L)1 inhibition was allowed. In phase 2, patients with hepatic metastases were not permitted unless they had been treated and were stable.

Phase 1 followed a traditional dose-escalation design in which patients received either 0.01 mg/kg, 0.02 mg/kg, 0.04 mg/kg, 0.08 mg/kg, 0.12 mg/kg, or 0.16 mg/kg of invikafusp alfa.¹ The dose expansion phase was broken into 3 cohorts: TMB-H (n = 56; cohort 1), MSI-H/dMMR (n = 29), and TMB-H and/or MSI-H/dMMR mCRC (n = 23 to 56). In phase 2, all patients received the recommended phase 2 dose (RP2D) of 0.08 mg/kg of the agent intravenously every 2 weeks.

The primary objective of phase 1 was to determine the RP2D and evaluate the safety and tolerability of the regimen. ORR per immune RECIST criteria served as the primary objective of phase 2.

What Patient Characteristics Were Presented?

As of July 9, 2025, 55 patients with TMB-H/MSI-H tumors had been enrolled in phase 2, adding to the 8 that had been enrolled in phase 1 at the optimal biologic dose. Represented tumor types (n = 63) included CRC (25.4%), non–small cell lung cancer (14.3%), head and neck squamous cell carcinoma (7.9%), gastric cancer (6.3%), breast cancer (4.8%), cutaneous cancer (4.8%), endometrial cancer (4.8%), melanoma (4.8%), anal cancer (3.2%), basal cell carcinoma (3.2%), gastroesophageal junction cancer (3.2%), pancreatic cancer (3.2%), bladder cancer (1.6%), cervical cancer (1.6%), duodenal adenocarcinoma (1.6%), esophageal cancer (1.6%), neuroendocrine carcinoma cells (1.6%), ovarian cancer (1.6%), prostate cancer (1.6%), thymic cancer (1.6%), and thyroid cancer (1.6%).

The median age was 61 (range, 53-69) and most patients were male (95.2%), White (63.5%), and had an ECOG performance status of 1 (52.8%). Most patients received between 1 and 3 prior lines of therapy (65.1%), prior treatment with an immune checkpoint inhibitor (67%), and had TMB-H disease (73.0%). Best response to prior immunotherapy was largely split between partial response (30.1%), stable disease (16.7%), progressive disease (26.2%), and unknown (26.2%).

Was the Agent’s Mechanism of Action Indicative of Its Safety Profile?

Italiano noted that the safety profile was consistent with the agent’s mechanism of action. The most common treatment-related adverse effects (TRAEs) were cytokine release syndrome (grade 1, 22.2%; grade 2, 46.0%; grade 3, 12.7%), rash (grade 1, 11.1%; grade 2, 34.9%; grade 3, 7.9%), nausea (grade 1, 28.6%; grade 2, 20.6%; grade 3, 1.6%), pruritus (grade 1, 22.2%; grade 2, 20.6%; grade 3, 6.3%), vomiting (grade 1, 17.5%; grade 2, 31.7%; grade 3, 0%), alanine aminotransferase increase (grade 1, 22.2%; grade 2, 4.8%; grade 3, 9.5%), platelet count decrease (grade 1, 11.1%; grade 2, 12.7%; grade 3, 12.7%), chills (grade 1, 15.9%; grade 2, 11.1%; grade 3, 0%), diarrhea (grade 1, 19.0%; grade 2, 6.3%; grade 3, 1.6%), peripheral edema (grade 1, 9.5%; grade 2, 7.9%; grade 3, 0%), and increased blood bilirubin (grade 1, 7.9%; grade 2, 4.8%; grade 3, 3.2%).

“No step-up dosing and no immune checkpoint inhibitor–type immune-related adverse effects were reported. TRAEs were on target and well managed with supportive care, including corticosteroids such as tocilizumab (Actemra),” Italiano said.

What Are the Key Takeaways From This Presentation?

“Selective activation of the T-cell Vβ repertoire represents a novel class of IO bispecific therapy, with broad potential as a next generation T-cell–targeted multi-specific antibody platform for the advancement of precision immunotherapy,” Italiano concluded.

Disclosures: No disclosures were presented for Italiano.

References

1. Garralda E, Italiano A, Marabelle A, et al. START-001: initial phase 2 clinical activity of invikafusp alfa, a first-in-class T cell receptor (TCR) β-chain-targeted bispecific antibody as monotherapy in patients with antigen-rich solid tumors resistant to immune checkpoint blockade (ICB). Presented at: 2025 ESMO Congress; October 17-21, 2025; Berlin, Germany. Abstract LBA55.
2. A study of a selective T cell receptor (TCR) targeting, bifunctional antibody-fusion molecule STAR0602 in participants with advanced solid tumors (START-001). Clinicaltrials.gov. Updated July 9, 2025. Accessed October 18, 2025. https://clinicaltrials.gov/study/NCT05592626

The combination of pembrolizumab (Keytruda) plus weekly paclitaxel with or without bevacizumab (Avastin) generated a statistically significant progression-free survival (PFS) benefit vs placebo plus paclitaxel with or without bevacizumab regardless of PD-L1 status, as well as an overall survival (OS) benefit, in patients with recurrent, PD-L1–expressing platinum-resistant ovarian cancer (PROC), according to data from the phase 3 ENGOT-ov65/KEYNOTE-B96 trial (NCT05116189) presented at the 2025 ESMO Congress.

The analysis was broken down between the population of patients with a combined positive score (CPS) of 1 or higher and the intention-to-treat population. Furthermore, data were broken down between interim analysis 1 (IA1), which had a data cutoff date of April 3, 2024, and interim analysis 2 (IA2), which had a data cutoff date of May 5, 2025.

The CPS of 1 or Higher Population

At IA1, the median PFS was 8.3 months (95% CI, 7.0-9.4) in the pembrolizumab arm compared with 7.2 months (95% CI, 6.2-8.1) in the placebo arm, with 12-month PFS rates of 35.2% (95% CI, 28.8%-41.7%) vs 22.6% (95% CI, 17.0%-28.7%), respectively (HR, 0.72; 95% CI, 0.58-0.89; P = .0014).

At IA2, the median PFS was 8.3 months in the pembrolizumab arm compared with 7.2 months in the placebo arm (HR, 0.75; 95% CI, 0.61-0.91); the 12-month PFS rates were 35.9% vs 23.9%, respectively, and the 18-month rates were 18.7% vs 10.5%.

The median OS was 18.2 months (95% CI, 15.3-21.0) in the pembrolizumab arm compared with 14.0 months (95% CI, 12.5-16.1) in the placebo arm, with 12-month OS rates of 69.1% vs 59.3%, and 18-month OS rates of 51.5% vs 38.9%, respectively (HR, 0.76; 95% CI, 0.61-0.94; P = .0053).

The objective response rate (ORR) was 53.0% (95% CI, 45.8%-60.0%), with a complete response (CR) rate of 9.9% and a partial response (PR) rate of 43.1%, in the pembrolizumab arm; in the placebo arm, the ORR was 46.6% (95% CI, 39.6%-53.7%), with a CR rate of 7.8% and a PR rate of 38.7%. The 12- and 18-month duration of response (DOR) rates in the pembrolizumab arm were 46.7% and 28.4% compared with 29.6% and 16.4% in the placebo arm.

The ITT Population

At IA1, the median PFS was 8.3 months (95% CI, 7.2-8.6) with pembrolizumab compared with 6.4 months (95% CI, 6.2-8.1) with placebo, with 12-month PFS rates of 33.1% (95% CI, 27.7%-38.5%) and 21.3% (95% CI, 16.6%-26.4%), respectively (HR, 0.70; 95% CI, 0.58-0.84; P <.0001).

At IA2, the median PFS was 8.3 months vs 6.4 months, respectively (HR, 0.73; 95% CI, 0.62-0.86); the 12-month PFS rates were 33.7% vs 22.5%, and the 18-month PFS rates were 17.3% vs 9.0%.

The ORR was 50.4% (95% CI, 44.3%-56.4%), with a CR rate of 8.3% and a PR rate of 42.0%, in the pembrolizumab arm; in the placebo arm, the ORR was 40.8% (95% CI, 35.0%-46.8%), with a CR rate of 6.0% and a PR rate of 34.8%.Furthermore, the 12- and 18-month DOR rates in the pembrolizumab arm were 46.6% and 26.5% compared with 28.4% and 14.5% in the placebo arm.

“These data support the use of pembrolizumab plus weekly paclitaxel, with or without bevacizumab, as a new standard of care for patients with [recurrent] PROC,” presenting author Nicoletta Colombo, MD, PhD, of the Gynecologic Oncology Program at the European Institute of Oncology, IRCCS, in Milan, Italy, and the Department of Medicine and Surgery at the University of Milan-Bicocca in Italy, wrote with coauthors in the presentation.

Safety Analyses

Any-grade treatment-related adverse events (TRAEs) occurred in 97.8% of the pembrolizumab arm and 95.3% of the placebo arm; grade 3 or higher TRAEs occurred in 67.5% and 55.3%, respectively. TRAEs were serious in 33.1% and 19.5%, led to death in 0.9% and 1.6%, and led to discontinuation of any treatment in 35.9% and 28.0%.

Any-grade immune-mediated AEs occurred in 39.1% and 18.9%, and grade 3 or higher events occurred in 11.6% and 3.5%. They were serious events in 10.9% and 2.2%, and led to treatment discontinuation in 6.9% and 2.5%.

The most common TRAEs in both groups included anemia (49.7% vs 42.1%, respectively), peripheral neuropathy (38.8% vs 31.1%), alopecia (37.8% vs 34.0%), fatigue (35.3% vs 33.0%), and nausea (31.3% vs 27.4%). The most common immune-mediated AEs were hypothyroidism (17.8% vs 6.0%), infusion reactions (5.9% vs 4.7%), and hyperthyroidism (5.0% vs 0.6%).

Trial Breakdown

A total of 643 patients with histologically confirmed epithelial ovarian, fallopian tube, or primary peritoneal carcinoma were enrolled in the trial and randomly assigned to either the pembrolizumab arm (n = 322) or the placebo arm (n = 321). Treatment was either pembrolizumab at 400 mg once every 6 weeks for 18 cycles or placebo on the same schedule; all patients received paclitaxel at 80 mg/m² on days 1, 8, and 15 of each 3-week-long cycle, and they either did or did not receive bevacizumab at 10 mg/kg every 2 weeks.

Patients were enrolled in the trial if they had received 1 or 2 prior lines of therapy with at least 1 platinum-based chemotherapy; prior anti-PD-1 or anti-PD-L1 agents, PARP inhibitors, and bevacizumab were permitted. Additionally, patients had radiographic progression within 6 months after the last dose of platinum-based chemotherapy and an ECOG performance status of 0 or 1.

The primary end point of the trial was PFS per RECIST v1.1 by investigator assessment, and a key secondary end point was OS.

The median age of patients was 62 years vs 61 years in the pembrolizumab vs placebo arm, 64.3% and 67.6% of patients were White, 41.3% and 41.1% had a PD-L1 CPS from 1 to less than 10, and 31.4% and 31.2% had a PD-L1 CPS of at least 10.

Reference

Colombo N, Zsiros E, Sebastianelli A, et al. Pembrolizumab vs placebo plus weekly paclitaxel ± bevacizumab in platinum-resistant recurrent ovarian cancer: Results from the randomized double-blind phase 3 ENGOT-ov65/KEYNOTE-B96 study. Presented at: European Society of Medical Oncology Congress 2025; October 17–20, 2025; Berlin, Germany. Abstract LBA3.