FDA grants Kazia Therapeutics’ paxalisib drug rare paediatric disease designation

Kazia Therapeutics (ASX: KZA) has been awarded Rare Pediatric Disease Designation (RPDD) for its lead drug paxalisib by the FDA for treating Diffuse Intrinsic Pontine Glioma (DIPG).

RPDD status means Kazia is now eligible to receive a what’s known as a “rare paediatric disease priority review voucher” (PRV) – a resaleable means of expediting a six-month review of a new drug application with the FDA – if paxalisib is approved to treat DIPG, a rare and highly aggressive childhood brain cancer.

Kazia has published several positive updates regarding paxalisib in treating the most common and aggressive form of primary brain cancer glioblastoma in recent weeks.

Meanwhile, phase 1 trials using the drug in treating DIPG began in October 2018 at St Jude Children’s Research Hospital in Memphis with favourable top-line safety data published in 2019.

This study has now completed recruitment with initial efficacy data expected to be published later this year – providing a guide for future development of paxalisib.

Commercialising paxalisib

In addition to glioblastoma and DIPG, three other studies are underway with paxalisib in different forms of brain cancer.

Kazia anticipates initial efficacy data from the other trials in the remainder of this year.

In a presentation to the American Association for Cancer Research (AACR) in June, Kazia revealed an interim analysis of its ongoing phase 2 study of paxalisib in glioblastoma. The company said its study determined a median overall survival of 17.7 months for patients treated with paxalisib, compared to the historical control of 12.7 months for patients treated with temozolomide, which is the existing standard of care.

Kazia said it had received “very positive data in recent months” in the glioblastoma studies, with the drug “on track” to commence a phase 3 study for registration, subject to ongoing funding discussions.

According to Kazia’s chief executive officer Dr James Garner, Kazia expects to enter the market “within the next few years”.

Currently, analysts estimate the addressable glioblastoma market to top US$1.5 billion per year, although the current developmental trend is moving towards addressing unmet needs which are largely “hindered by difficulties in clinical development”, according to a report published by GlobalData.

RPDD program

The FDA integrated the RPDD program into its operations in 2012, to further the development of drugs treating serious and life-threatening rare paediatric diseases by providing incentives to private pharma companies.

Typically, RPDD status is granted for drugs treating diseases affecting young children, with an annual incidence of less than 200,000 in the US and which are serious or life-threatening.

According to Kazia, PRV represents the “most significant” incentive at the time of a marketing authorisation for the rare paediatric disease and cited past cases where PRVs were sold for “tens to hundreds of millions of dollars”.

The PRV effectively shortens the FDA review period for a future marketing application of any drug from 12 months to six, with Kazia optimistic that it could potentially offload its PRV to a large company launching a billion-dollar drug.

“For patients diagnosed with DIPG, there are currently no FDA-approved drug treatments, and the average survival from diagnosis is around 9.5 months,” Dr Garner said.

“The granting of RPDD by the FDA recognises our efforts and achievements so far and leaves us well placed to move paxalisib forward as a potential therapy for DIPG. We continue to be inspired by the dedication of our collaborators in this field and are committed to understanding whether paxalisib may be able to help in this enormously challenging paediatric disease.”

Moreover, there may soon be other applications for paxalisib further down the track.

“Although glioblastoma remains our primary focus for paxalisib, we have been devoting increasing energy to developing the drug in childhood brain cancer as well,” Dr Garner said.