Prescient Therapeutics Ltd (ASX:PTX) continues to demonstrate a favourable safety profile with its PTX-100 Phase 1b expansion cohort targeting relapsed and refractory T cell lymphoma (TCL) – and is also delivering on the clinical front.
The study shows that PTX-100 continues to exhibit an excellent safety profile at the highest dose of 2000 mg/m2.
Encouraging clinical activity
More importantly, PTX-100 also continues to show encouraging clinical activity in a difficult to treat patient population, including a striking response in a patient with refractory cutaneous TCL (CTCL).
“We continue to see impressive responses in both systemic and cutaneous T cell lymphomas on this study,” principal investigator of the study and globally renowned haematologist Professor H Miles Prince said.
“Furthermore, PTX-100 continues to be extremely well tolerated by patients. We look forward to continue accruing patients to the trial who otherwise have limited treatment options.”
Phase 1b enrolment
The expansion cohort has targeted eight to 12 patients. Eight patients have been screened and seven patients have been dosed with PTX-100 in the expansion cohort so far, including four with peripheral TCL (PTCL) and three with CTCL.
Before joining the trial, patients had received a median of four prior lines of therapy and up to six prior lines of therapy.
Four patients remain on therapy and additional patients are being recruited.
Excellent safety
The company welcomes the news that PTX-100 continues to exhibit an excellent safety profile, with very few adverse events in the expansion cohort so far, and no serious adverse events related to PTX-100.
Two PTCL patients that had commenced therapy withdrew from the study for reasons unrelated to the trial, while another PTCL patient passed away due to reasons not associated with the study, which is not uncommon in studies of advanced malignancies.
In each of these cases, subjects were not on the study long enough to observe responses. Relevant pharmacokinetic and safety data were still collected, in accordance with the primary objectives of the study.
Clinical outcomes
The primary goal of the expansion cohort is to evaluate safety but PTX-100 continues to exhibit encouraging clinical activity in the difficult-to-treat patient population.
Some of the responses the study has observed include:
- Patient 121-003 (previously reported in dose escalation component of the study) with aggressive PTCL that had failed five prior treatments, had a partial response that endured for over 32 months before the disease progressed.
- Patient 121-010 with CTCL that had failed four prior lines of therapy experienced a very good partial response (VGPR), which is almost a complete response that has endured for six months so far, and remains on therapy.
- Another two patients with CTCL that failed three prior therapies have experienced stable disease that have endured for three to four months so far and remain on therapy.
In light of these encouraging responses, Prescient has amended the study protocol to allow for the recruitment of additional CTCL patients.
The study will remain open while patients continue to derive clinical benefit from PTX-100. The company looks forward to providing further details on the expansion cohort study in the coming quarter.
Prescient CEO and managing director Steven Yatomi-Clarke said: “It is very exciting to see PTX-100 show clinical activity in a patient population that is notoriously difficult to treat, and where these patients have failed several lines of prior therapies.
“Furthermore, PTX-100 continues to exhibit an excellent safety profile, which is uncharacteristic of available TCL therapies.
“It is exciting to see encouraging responses in CTCL patients, alongside PTCL patients, and we will aim to recruit more CTCL patients to the study. We look forward to sharing these updates with the market.”