Trailing AstraZeneca and Merck, Junshi reports phase 3 ovarian cancer success for Lynparza rival

Junshi Biosciences has established its credentials as the next challenger for the increasingly congested Chinese PARP inhibitor market. A phase 3 trial of the candidate hit its primary endpoint, setting Junshi up to compete with products including AstraZeneca and Merck & Co.’s Lynparza for the ovarian cancer space. 

AstraZeneca and Merck won the first approval for a PARP inhibitor in China in 2019, but their monopoly on the market was short-lived. The next year, Zai Lab won approval for GSK’s Zejula and Jiangsu Hengrui Pharmaceuticals got the green light to sell AiRuiYi. BeiGene joined the party in May 2021. The drugs have slightly different labels and, according to a 2022 paper, Lynparza and Zejula are the most widely used. 

Despite the thicket of competitors, Junshi sees an opportunity for another PARP inhibitor. The Chinese drug developer secured access to a candidate, senaparib, in 2020 by forming a joint venture with Impact Therapeutics. 

At the time of the deal, Impact was eight months into a phase 3 clinical trial designed to show senaparib extends progression-free survival when given as a maintenance therapy to BRCA-positive ovarian cancer patients after first-line chemotherapy. The top-line findings, released late Tuesday in the U.S., showed the primary endpoint met the predefined efficacy boundary. 

The top-line data release lacks the figures behind the hit on the primary endpoint and details of how the drug candidate performed on other measures of safety and efficacy. Junshi thinks it has the data to file for approval, though, and plans to work with Impact to engage with regulators “in the near future.”

In the absence of data from the trial, it is hard to gauge how senaparib is likely to fare in a market with established incumbent products, but the little that is known points to some potential ways for Junshi and Impact to try to differentiate the treatment. 

Jianjun Zou, president of global research and development at Junshi, hailed the trial as “the first phase 3 clinical study of a domestically developed PARP inhibitor that has achieved positive results for advanced ovarian cancer maintenance treatment following first-line therapy” in a statement. Zou added that the PARP inhibitor significantly extended progression-free survival regardless of BRCA mutation status. BRCA mutation, according to local pathological diagnosis, was on the inclusion criteria for the clinical trial.

AiRuiYi was the first domestically developed PARP inhibitor to hit the Chinese market, but its approval in 2020 was limited to patients with the germline BRCA mutation who had undergone second-line or above chemotherapy. Zejula was the first PARP drug approved in China in first-line and recurrent maintenance treatment settings regardless of biomarker status, but it originated outside of the country.