Animal study shows Patrys’ breast cancer drug can suppress secondary tumours and complement radiation

A pre-clinical animal study using Patrys Limited’s (ASX: PAB) lead candidate drug PAT-DX1 has shown the drug can significantly suppress the growth of secondary brain tumours in patients with triple negative breast cancer (TNBC), even with a shortened dosing regimen.

Brain tumours develop in up to 50% of patients with metastatic TNBC and can have serious impacts on neurologic function and survival rates.

Patrys’ latest study was conducted by doctors from the Yale School of Medicine and builds on the findings of a precursor study conducted last year which demonstrated that PAT-DX1 administered systemically could significantly reduce TNBC brain metastasis proliferation and improved survival.

In the pre-clinical animal study which focused on shortened doses, PAT-DX1 was administered for just one weekly cycle of three doses, compared to precursor doses of four weekly cycles (12 doses in total).

Results showed that even with the reduced and shortened dosing regimen, PAT-DX1 was able to significantly suppress TNBC brain metastases after just one week of treatment, with responses maintained for several weeks after drug administration was discontinued.

It showed that PAT-DX1 is able to cross the blood-brain barrier with no toxicity and that the drug could suppress tumour growth in a similar way as low-dose radiation treatment.

Importantly, a combination of PAT-DX1 and radiation treatment could result in significantly greater tumour suppression than either treatment used on its own.

A substantial advance

Patrys chief executive officer Dr James Campbell said the study results are a step in the right direction for the drug’s ongoing development.

“Our drug crosses the blood brain barrier and shows single agent efficacy in sophisticated animal models of TNBC brain metastases,” he said.

“We are not aware of any other antibody which brings together these transformative attributes – it represents another substantial advance in our understanding of the dosing and possible clinical applications for PAT-DX1.”

Dr Campbell said the drug could potentially improve patient outcomes where there remains a “large unmet medical need” for TNBC brain metastases.

Most aggressive cancer

Breast cancer remains a leading cause of cancer death in women, with industry figures showing approximately 1.67 million new cases are diagnosed worldwide each year.

Subtypes of breast cancer are stratified in accordance with their expression of estrogen, progesterone and HER2 (human epidermal growth factor receptor 2).

Tumours which lack all three receptors are identified as TNBC and represent up to 20% of all breast cancer cases.

TNBC is believed to be the most aggressive and difficult breast cancer to treat, with an inability to cross the blood brain barrier creating an obstacle for many potential therapeutics.

The global market for TNBC was US$296 million in 2015, and is expected to increase to US$1.59 billion by 2025.

Patrys and Yale are now planning additional studies to explore the interactions between different radiation and PAT-DX1 dosing regimens which will inform and guide the drug’s clinical development.

At midday, shares in Patrys Limited were up 25.93% to $0.034.