FDA clears Precigen's rare tumour immunotherapy

Precigen has won approval in the US for a first-in-class immunotherapy for recurrent respiratory papillomatosis (RRP), a rare, benign tumour that can cause significant health challenges.

Papzimeos (zopapogene imadenovec; formerly PRGN-2012) is a subcutaneously administered, non-replicating adenoviral vector-based immunotherapy designed to elicit immune responses against cells infected with two strains of human papillomavirus (HPV) that cause RRP.

The disease, associated with HPV 6 and HPV 11 infection, causes growths in the respiratory tract, most commonly the larynx, that can result in voice changes, breathing difficulties, and airway obstruction. There are no approved medical therapies for RRP, other than repeated surgeries to remove the tumours.

There are around 1,000 new cases of RRP each year in the US, according to the FDA, while Precigen has estimated that around 27,000 adult Americans are living with the condition.

Papzimeos' approval is the first to emerge from the FDA's Center for Biologics Evaluation and Research (CBER) since Vinay Prasad rejoined as director, shortly after leaving the post amid a smear campaign by right-wing activists in the US.

Approval of Precigen's biologics license application (BLA) stemmed mainly from an open-label clinical trial, reported at this year's ASCO congress and published in The Lancet Respiratory Medicine, which revealed a complete response rate in 18 (51%) of the 35 subjects enrolled, defined as no requirement for surgery in the 12 months following completion of treatment.

Each of them had had a minimum of three surgeries in the prior 12 months and received four injections of Papzimeos, and 30 (86%) saw a decrease in the need for procedures in the 12 months after the treatment.

"Randomised trials are not always needed to approve medical products and this approval is proof of that philosophy," said Prasad in a statement.

"The FDA will always demand the correct clinical study for the specific medical product and disease," he added. "Our requirements for products given to tens of millions of healthy people will be different than products given to at most hundreds or thousands of patients with unique diseases."

The company is currently enrolling patients into a trial designed to confirm the benefit of Papzimeos, which the FDA said had to have started before the BLA was filed.

Papzimeos is the first approved treatment to emerge from Germantown, Maryland-based Precigen and its off-the-shelf AdenoVerse gene therapy platform, with a follow-up programme (PRGN-2009) targeting HPV-associated cervical and oropharyngeal cancers in phase 2.

The company raised $87.5 million in a private placement last December, ending 2024 with just under $98 million in cash reserves, which it said would fund the company through the launch of Papzimeos.