Phase 2 Trial Testing Darinaparsin Completes Enrollment of Asian Patients with Relapsed or Refractory PTCL

A Phase 2 clinical trial assessing Solasia Pharma’s lead candidate darinaparsin as a treatment for relapsed or refractory peripheral T-cell lymphoma (PTCL) in Asian patients has reached its target enrollment, the company announced.

The Asian multinational study (NCT02653976) has recruited 67 patients across 24 sites in Japan, Hong Kong, South Korea, and Taiwan. Every three weeks, participants will receive an injection of darinaparsin (300 mg/m²) once daily for five consecutive days. Each treatment cycle will be repeated up to six times.

The trial’s main goal is to assess tumor response, or the proportion of patients seeing a reduction in tumor burden after treatment. Secondary measures include progression-free survival (the time patients live without disease worsening), overall survival, and safety.

If the results of this pivotal trial are positive, the company is expected to apply for the treatment’s marketing approval in Japan. Results are expected in 2020.

Darinaparsin, formerly known as SP-02L, is a small molecule compound that targets the activity of mitochondria — the cell’s powerhouses — and triggers the death of cancer cells. It remains unclear how darinaparsin works, but studies in experimental and animal models showed that darinaparsin and its intermediate compounds are highly toxic to cells.

Arsenic compounds generated from darinaparsin metabolization can disrupt the normal activity of mitochondria, induce production of damaging oxidative elements, arrest cell proliferation, and prevent formation of new blood vessels — all essential features for cancer progression.

In a previous Phase 2 clinical trial (NCT00421213) conducted in the U.S., darinaparsin treatment led to encouraging responses in lymphoma patients, most of whom were heavily treated or had few other treatment options available.

The compound had the most promising results in a subgroup of patients with PTCL, who had a clinical benefit rate of 80%. Among seven patients included, one had a complete response, one had an unconfirmed complete response, and two had prolonged disease stabilization.

Based on the findings, darinaparsin received orphan drug designation by the U.S. Food and Drug Administration and the European Medicines Agency for the treatment of PTCL.

In Korea and Japan, two Phase 1 studies (NCT01689220 and NCT01435863) have also shown that darinaparsin treatment is safe and well-tolerated, and induces strong anti-cancer responses in relapsed or refractory PTCL patients. Solasia is also planing to pursue orphan drug status for darinaparsin in Japan.