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Phase II trial of oral pamiparib in recurrent ovarian cancer after prior PARPi exposurePamiparib alone offers limited hope for ovarian cancer patients who have already tried other drugs

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Key Takeaway
Note preliminary efficacy of pamiparib in recurrent ovarian cancer after prior PARPi exposure in a small cohort.

This prospective Phase II clinical trial evaluated oral pamiparib 60 mg twice daily in a population of 15 patients with recurrent ovarian cancer after prior PARPi exposure. The study setting was not reported. The primary outcome was the clinical benefit rate of at least 4 months. Secondary outcomes included progression-free survival, overall response rate, overall survival, and safety.

Main results indicated a clinical benefit rate of 26.7% for the overall population. The overall response rate was 13.3%, with 2 patients achieving partial response. In the BRCA-mutated cohort, the clinical benefit rate was 37.5% (3 of 8 patients), while the BRCA-wild-type cohort showed a rate of 14.3% (1 of 7 patients). Median progression-free survival was 2.8 months with a 95% CI of 1.6 to not reported. Median overall survival was 15.6 months with a 95% CI of 8.4 to not reported. The CA-125 response rate was 26.7%.

Safety and tolerability were assessed, with no treatment-related serious adverse events reported. The safety profile was described as acceptable. Discontinuations were not reported. However, the study was halted in the first stage according to pre-set statistical criteria. The study type was a prospective clinical trial, not an RCT.

Practice relevance suggests that single-agent pamiparib retreatment may not be an effective treatment for this patient population. Further investigation of combining PARPi with agents with different mechanisms may be warranted. The certainty of these findings is preliminary.

Imagine a woman named Sarah. She has fought ovarian cancer for years. Her doctors gave her strong medicines. They gave her platinum chemo. Then they gave her a PARP inhibitor. Now her cancer has come back. Her options are running low. She needs a new path forward.

Ovarian cancer is a tough disease. It often returns after the first round of treatment. Many women face a situation where standard drugs no longer work. This leaves doctors and patients searching for something new. The goal is always to stop the cancer from growing.

But here is the twist. A new drug called pamiparib looks promising on paper. It belongs to the same family as the PARP inhibitors women already use. Doctors hoped it would work even after other drugs failed. They wanted to know if taking it alone would help.

Think of cancer cells like a factory. They need certain parts to keep running. PARP inhibitors cut off one of those parts. The cancer tries to fix itself but fails. Now imagine the cancer has found a way to bypass that cut. It uses a different part to survive. This is what happens in resistant cancer.

The study looked at fifteen women. They took part between August 2022 and December 2023. Each woman had already used platinum chemo and a PARP inhibitor. They took oral pamiparib twice a day. They kept taking it until the study stopped or their cancer grew.

The main goal was simple. Did the drug keep the cancer stable for at least four months? Only one in four women met this goal. Two women saw their tumors shrink. This means the overall response rate was low. The drug did not work for most people in this small group.

This doesn't mean this treatment is available yet.

The study had to stop early. The numbers did not meet the statistical targets set before the trial began. This is a hard reality for patients hoping for a miracle. The median time before cancer grew was less than three months. This is not the long-term control many women need.

Some women did have better results. Those with a specific gene mutation called BRCA mutation saw higher success rates. About three out of eight women in this group benefited. Others without this mutation saw very little help. This suggests the drug might work better for some specific types of cancer.

Safety was not a major concern. No serious side effects happened during the trial. No deaths were linked to the drug itself. This is good news because it means the drug is not dangerous. The problem is simply that it does not stop the cancer for most people.

Experts say this result changes how we think about retreatment. Using the same type of drug alone might not be the answer. The cancer has likely built up resistance to this mechanism. Doctors now suspect we need to mix drugs with different ways of attacking the cancer.

What does this mean for Sarah? She might need to talk to her doctor about combination therapies. Waiting for a single drug to work alone might waste precious time. The research team suggests trying other agents alongside pamiparib. This approach could unlock the potential of the drug.

The study has limits. Only fifteen women took part. This is a very small number. Results from small groups can change with larger studies. The data comes from a single center too. More research is needed to confirm these findings across different hospitals.

The road ahead is clear. Researchers will likely test pamiparib with other drugs. They will look for the right partners to fight resistant cancer. This trial shows that single-agent use is not enough. The future lies in combining treatments to hit the cancer from multiple angles.

Patients should discuss their specific situation with their oncology team. Every case is different. What works for one person may not work for another. Trust the medical process but stay informed about new options. Research moves slowly but steadily toward better outcomes.

Study Details

Study typePhase2
EvidenceLevel 3
PublishedMay 2026
View Original Abstract ↓
AIM: To evaluate the efficacy and safety of pamiparib monotherapy in recurrent ovarian cancer (rOC) after prior PARPi exposure. METHODS: This was a prospective clinical trial. Fifteen patients were enrolled between August 2022 and December 2023. Oral pamiparib 60 mg twice daily was administered until conditions specified in the protocol. Primary endpoint was clinical benefit rate ≥ 4 months (CBR4m; percentage of patients who sustained complete response, partial response [PR], and stable disease for at least 4 months). Secondary endpoints included progression-free survival (PFS), overall response rate (ORR), overall survival (OS), and safety. RESULTS: Median number of previous treatment line was 3 (range, 2-6). CBR4m was 26.7% and the study was halted in the first stage according to the pre-set statistical criteria. Two patients achieved PR for an ORR of 13.3%. With a median follow-up of 16.1 months, median PFS and OS were respectively 2.8 (95% confidence interval [CI], 1.6-NR) and 15.6 (95% CI, 8.4-NR) months. Subgroup analyses showed CBR4m of 37.5% (3/8) in BRCAmut and 14.3% (1/7) in BRCAwt cohorts. CA-125 response according to GCIG criteria was observed in 26.7% of patients. There were no treatment-related serious adverse events or deaths. CONCLUSIONS: Pamiparib monotherapy preliminarily showed limited efficacy and acceptable safety profiles in heavily pretreated rOC after prior PARPi exposure. The results suggested that single-agent pamiparib retreatment may not be an effective treatment for this patient population; further investigation of combining PARPi with agents with different mechanisms may be warranted.
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