Key Clinical Summary:

• Design/Population: An ongoing phase 1b/2, open-label single-arm trial evaluated LB-100 plus dostarlimab in patients with platinum-resistant ovarian clear cell carcinoma who were MMR-proficient and PPP2R1A wild-type, who received a median of 2 prior lines of therapy.
• Key Outcomes: The combination achieved an objective response rate of 26.3% with durable responses and encouraging survival rates. Treatment-related grade ≥ 3 adverse events occurred in 20% of patients.
• Clinical Relevance: LB-100 plus dostarlimab demonstrates promising activity and manageable safety. These results support further evaluation of PP2A inhibition to enhance immunotherapy efficacy and the development of biomarker-driven strategies.

Results from an ongoing, phase 1b/2 trial demonstrate that the addition of the PP2A inhibitor LB-100 to dostarlimab shows encouraging clinical efficacy with manageable safety among patients with platinum-resistant ovarian clear cell carcinoma. 

These findings were presented by Helen Clark, MD, MD Anderson Cancer Center, Houston, Texas, at the 2026 Society of Gynecologic Oncology (SGO) Annual Meeting in San Juan, Puerto Rico.

In this open-label, single-arm study,  20 patients with mismatch repair-proficient, PPP2R1A wild-type platinum-resistant ovarian clear cell carcinoma who had received a median of 2 prior lines of therapy received 2.33 mg/m² of LB-100 on days 1 to 3 of each 3-week cycle plus 500 mg of dostarlimab every 3 weeks for 4 cycle followed by 1000 mg every 6 weeks thereafter until disease progression, unacceptable toxicity, or for up to 24 months. The primary end point was 6- and 12-month overall survival (OS). Key secondary end points included objective response rate (ORR), duration of response, and disease control rate. 

At a median follow-up of 10.7 months, median OS was not reached. The estimated 6-month OS probability was 0.83 and the estimated 12-month OS probability was 0.75. The ORR was 26.3% with a disease control rate of 42.1% and a median duration of response of 11.6 months. Exploratory analysis results showed that patients with somatic TERT promoter mutations (n = 9) had a stable disease rate of 66% and a parital response rate of 20% (P = .05), indicating a potential molecular correlate of benefit. 

There were 7 patients who remained on study treatment at time of analysis and patients received a median of 4.5 cycles. No new unexpected safety signals were observed and grade ≥3 treatment-related adverse events were reported in 20% of patients. The most frequently reported adverse event was ALT elevation.

 “These findings support PP2A inhibition as a rational strategy to potentiate the effects of ICB and warrant continued investigation of LB-100–ICB combinations along with biomarker-driven correlative analyses,” concluded Dr Clark et al. “An additional cohort with a higher exposure to LB100 is enrolling.” 

Source:

Clark H, Hinchcliff E, Al Ansarri H, et al. Combination PP2A inhibition and PD-1 blockade with LB-100 and dostarlimab in ovarian clear cell carcinoma. Presented at SGO Annual Meeting on Women’s Cancer. April 10 - 13, 2026; San Juan, Puerto Rico. LBA8.