Kazia Therapeutics reveals 100% response rate in interim data from brain metastases drug trial

Oncology-focused drug developer Kazia Therapeutics (ASX: KZA) has presented promising new data from an ongoing phase one clinical trial of its lead drug paxalisib in combination with radiotherapy for the treatment of brain metastases.

Interim data from the first stage of the study, led by Dr Jonathan Yang at the Memorial Sloan Kettering Cancer Centre in New York, reported all nine evaluative patients experienced complete or partial response to the treatment, representing an overall response rate of 100%.

Kazia said this can be compared to a typical overall response rate associated with whole brain radiotherapy alone, which commonly ranges from 20-45% in published studies.

Kazia chief executive officer Dr James Garner said the company is encouraged by the data and by the potential benefit it may indicate to this “substantial and high-need” group of patients.

“Radiotherapy is a ubiquitous component of the treatment paradigm for brain metastases, but resistance is common. Dr. Yang’s study has shown a very promising signal that paxalisib may help to potentiate the effect of radiotherapy.”

Recruitment of an additional 12 patients for the second stage of the study is already underway and Kazia expects preliminary data from this expansion stage in 2023.

Dr Garner also revealed that the ongoing Alliance study in brain metastases has graduated to an expansion stage in the breast cancer cohort.

“This now represents the second positive signal for paxalisib in brain metastases, which we increasingly believe represents a very promising opportunity for the product candidate,” he said.

Interim results

Kazia’s phase one paxalisib trial is designed in two stages: an initial exploratory stage and a confirmatory expansion stage.

Patients in the trial to date have comprised a range of primary tumours, with breast cancer being the most common, representing one-third of patients.

Of the 12 patients recruited in the initial stage, nine were evaluable for efficacy. All nine exhibited “complete or partial response” to the combination therapy of paxalisib and radiotherapy.

According to Kazia, the safety profile of paxalisib in combination was broadly consistent with monotherapy experience in other clinical trials, and a maximum tolerated dose of 45mg daily in combination with radiotherapy was confirmed.

Data to be presented at conference this week

This interim data has been accepted for a presentation at the upcoming 2022 Annual Conference on CNS Clinical Trials and Brain Metastases to be held in Toronto, Canada later this week.

Kazia said its next steps following the expansion stage will be to discuss emerging data from the study, along with other research in brain metastases, with scientific advisors and regulatory consultants with potential FDA consultation at a future date.

Around one-fifth of all cancer patients will develop brain metastases

According to Kazia, around 20% of all patients with cancer will develop secondary tumours in the central nervous system, known as brain metastases. The most common primary tumours that spread to the brain include lung, breast, colorectal, melanoma, and renal cell carcinoma.

Approximately 200,000 cancer patients develop brain metastases in the United States each year. They are usually managed by radiotherapy but are typically very challenging to treat and are associated with poor prognosis.