Specialty pharmaceutical company Race Oncology (ASX: RAC) has reported positive data from an investigator-initiated Phase II clinical trial of historical cancer drug Bisantrene on patients with relapsed or refractory acute myeloid leukaemia.
Conducted at the Sheba Medical Centre in Israel, the open-label, single-agent trial studied 10 patients who, on average, had failed three prior lines of treatment.
Bisantrene was found to be well tolerated with no unexpected or serious toxicities, the company reported.
After a single course of treatment, the drug demonstrated an overall clinical response rate of 40%, with one patient progressing to complete remission and three achieving partial remission.
One patient was bridged to allogeneic stem cell transplantation (where cells are donated to the patient from a genetically-matched donor) and there were no removals or withdrawals from the study during treatment.
The drug also had marked activity in four patients with extramedullary (outside of the bone marrow) acute myeloid leukaemia – such as leukemia cutis, chloromas, and central nervous system disease – which has historically been difficult to treat.
The most frequently reported serious adverse events were thrombocytopaenia (low blood platelets) and mucositis (mouth ulcers), both of which were expected side effects of anthracyline and anthracene chemotherapeutics.
One patient experienced transient grade one kidney toxicity and there were no liver toxicities observed.
Race said there were no anaphylactoid-type reactions observed in any patient over the course of treatment. This type of reaction was a serious adverse event regularly observed in the historical trials.
Relapsed or refractory acute myeloid leukaemia remains a significant therapeutic challenge.
While meaningful gains have been achieved in recent years with the introduction of new targeted drugs, published studies claim the clinical outcomes remain unsatisfactory.
Bisantrene is a small molecule cancer drug related to anthracyclines – the most widely-used class of chemotherapy drugs.
Unlike anthracyclines, it has a greatly reduced risk of cardiotoxicity (heart damage), meaning it can be used with patients who have reached their cardiotoxic limit with anthracyclines, or cannot tolerate anthracyclines due to existing heart conditions, age or other factors.
Bisantrene was tested in more than 40 phase II clinical trials during the 1980s and 1990s with up to $200 million put into its development, before it was “lost” in a series of big pharmaceutical mergers.
Race clinical advisory board chairman and international authority in clinical leukaemia and stem cell research, Professor Borje Andersson, said the trial confirmed historical results which used a different formulation of Bisantrene.
“While Bisantrene had been demonstrated in the 1980s as an effective salvage drug against acute myeloid leukaemia, the [clinical] data we had was old,” he said.
“It was important for us to study it by today’s standards using the current formulation, so we could confirm whether our strategy of repurposing this drug is sound.”
“We also wanted to confirm that Bisantrene could still generate a meaningful response rate in a highly-frail patient population with heavily pre-treated acute myeloid leukaemia,” Professor Andersson added.
The study saw a reduction in the leukaemic disease burden and an overall response rate in 40% of the patients.
“While we must study the drug further, it appears that with this kind of response, Bisantrene-based therapy may have the potential to serve as an important bridge to allogeneic stem cell transplantation in patients who otherwise have few therapeutic options,” Professor Andersson said.
Race chief scientific officer Dr Daniel Tillett said a key focus of Phase II clinical trial was to determine Bisantrene’s safety in a modern context.
“These results are pleasing from a safety and activity perspective, particularly given the clinically-challenging patient population included in the trial,” he said.
“It was encouraging to see the drug’s tolerability profile compared favourably with other commonly-used chemotherapy agents such as anthracyclines, while the side effects were in keeping with what we would expect to see with all chemotherapeutics of this class,” Dr Tillett added.
Professor Andersson said the trial found Bisantrene to be an agent with an acceptable safety profile and promising anti-leukaemic activity.
“As this was an open-label, single-agent trial, we can be confident that it was the Bisantrene exposure which generated the positive results,” he said.
“The patient cohort had advanced acute myeloid leukaemia and had previously failed an average of three lines of therapy, so they were always going to be tough to treat, but a 40% overall response rate after only a single course of treatment markedly exceeded our expectations.”
“It is a hugely promising result and one which reinforces our development plans for this drug,” Professor Andersson added.
A follow-up study combining Bisantrene with other anti-leukaemic drugs is currently in the advanced planning stages.
At mid-morning, shares in Race Oncology were up 53.97% to $0.485.