Prescient Therapeutics Ltd (ASX:PTX, OTC:PSTTF) has presented results of its Phase 1b study of PTX-100 in patients with advanced malignancies to the prestigious American Society of Hematology (ASH) Annual Meeting in San Diego, California, with the study demonstrating excellent safety and promising efficacy in T-cell lymphoma patients.
With a focus on patients with relapsed and refractory T-cell lymphomas (r/r TCL), the study — involving 25 patients, including 19 r/r TCL patients — successfully achieved its primary objectives of demonstrating safety and determining pharmacokinetics (PK) and pharmacodynamics (PD). It also successfully demonstrated preliminary efficacy in r/r TCL patients exceeding that expected from standard of care.
Now that Phase 1b recruitment is complete — although several patients remain on study — Prescient is working diligently towards a Phase 2 trial in r/r TCL, which is due to start around mid-2024.
Phase 1 study surpasses expectations
This Phase 1 study aimed to evaluate the safety, PD and PK, and preliminary efficacy of PTX100 administered in increasing doses in patients with advanced malignancies. Given that efficacy was observed early in patients with r/r TCL, this patient population became the focus of an expansion cohort.
“Prescient is very pleased with the data from this Phase 1b study in patients with relapsed and refractory TCL," said Prescient CEO and managing director Steven Yatomi-Clarke.
"The data has surpassed our expectations from both safety and early efficacy perspectives, especially in this difficult-to-treat patient population. The team is working judiciously with its advisors in planning and working towards the Phase 2 study, which Prescient believes will be a watershed moment for the company.”
Successful results
This Phase 1b trial successfully met its objectives, with PTX-100 indicating a promising safety profile — especially in light of the fragile patient population and the relatively high toxicities of many incumbent therapies for r/r TCL — and is well-tolerated up to 2,000 mg/m2 in this difficult to treat patient population.
PD studies demonstrated that PTX-100’s target, GGT-1, was engaged at all three doses with sustained inhibition demonstrated over 72 hours after the day five dose.
Although efficacy was not the focus of the Phase 1b study, clinical activity was demonstrated in evaluable r/rTCL patients with an ORR of 44% (4/9), and a median PFS of 12.2 months.
This compares very favourably with responses expected using standard-of-care therapies in this patient population, which is generally expected to be an ORR of around 30% and median PFS of four months.
“A beacon of hope for patients”
Professor H. Miles Prince AM, principal investigator of the study and globally renowned haematologist said, “These Phase 1b results highlight the excellent tolerability of PTX 100 among TCL patients. Beyond monotherapy, PTX’s excellent safety profile makes it a viable option for exploring combination therapies in the future.
“In addition to PTX-100’s safety, early indications suggest promising efficacy in both systemic and cutaneous T cell lymphomas, as evidenced by several patients exhibiting clinical responses and others demonstrating durable stable disease. Notably, the median PFS of 12.2 months surpasses the usual expectations associated with standard care treatments, which typically yield a median PFS of around four months.
“This compelling outcome fuels my enthusiasm to advance into a Phase 2 study. I am hopeful that expanding this research will provide a beacon of hope for patients facing limited treatment options and poor anticipated outcomes.”
Looking ahead to Phase 2
Following the success of the Phase 1 study, Prescient is now planning a Phase 2 study in r/r TCL.
The company is currently designing the study with input from key opinion leaders and regulatory consultants ahead of an FDA meeting in the first or second quarter of next year, with the aim of opening the study around mid-year. A manufacturing campaign is also underway to supply this study.