PTC Therapeutics nabs 'phase 3 ready' biotech Censa for just $10M upfront plus stock

PTC Therapeutics is adding to its rare disease pipeline with a midstage biotech buyout with a low upfront payment tied in with stock and biobucks.

The company is Censa Pharmaceuticals, a little-known biotech that late last year reported encouraging data from a phase 2 study of its asset CNSA-001 (sepiapterin), an experimental med set up for orphan metabolic diseases including phenylketonuria (PKU) .

PKU is a rare, inherited metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene. Patients with mutations in the PAH gene inefficiently metabolize phenylalanine (Phe), leading to potentially toxic levels of Phe in the blood and serious resulting health problems.

By buying Censa, it’s setting itself up against rival biopharma BioMarin, which has two drugs on the market for PKU: most recently the injectable Palynziq and the much older Kuvan. In its phase 2 readout last December, sepiapterin beat out Kuvan and met its primary and secondary endpoints, achieving a statistically significant and clinically meaningful reduction in blood Phe levels compared to both baseline and BioMarin’s aging med.

BioMarin is, however, now working on a gene therapy for the disease and plotting a clinical trial this year, though COVID-19 has already pushed back timelines.

Censa's (now PTC’s) drug, an oral formulation of synthetic sepiapterin, is also being worked on in other diseases associated with defects in the tetrahydrobiopterin biochemical pathways diagnosed at birth.

PTC clearly likes what it sees, paying just $10 million upfront and buying around $40 million in stock, with $217.5 million in biobucks also wedded to the deal. After the midstage success, the biotech said that sepiapterin is now “phase 3 ready.”

This also includes the receipt of a priority review voucher as well as $30 million to be paid in either cash or PTC common stock for completing the enrollment of the phase 3.

“Results from a Phase 2 clinical trial of CNSA-001 demonstrated significant and clinically relevant reductions in phenylanaline levels compared to current first-line treatment,” said Stuart Peltz, Ph.D., CEO at PTC.

“We believe that CNSA-001 has the potential to address the majority of PKU patients whose condition is not adequately managed by current treatments. We look forward to initiating a Phase 3 study in PKU so that patients diagnosed with this devastating condition can have a new oral treatment option as soon as possible.”

This adds to PTC’s pipeline, which includes early work around gene therapy, nonsense mutation, splicing and oncology, with targets including Huntington’s disease, Angelman syndrome, relapsed/refractory acute leukemias, ovarian cancer and others.

PTC markets Emflaza, a controversial Duchenne muscular dystrophy (DMD) treatment, in the U.S. It sells another DMD drug, Translarna, in Europe, and Tegsedi, which treats polyneuropathy of hereditary transthyretin-mediated amyloidosis, in Latin America.

It also has a 2020 date with the FDA for a potential approval for its Roche-partnered spinal muscular atrophy therapy risdiplam, which will compete with the likes of Biogen and Novartis but could still be a solid blockbuster at peak.

“I am proud of the team at Censa and its achievements to date demonstrating the potential role of CNSA-001 in treating diseases of the BH4 pathway," said Jonathan Reis, M.D., president and CEO of Censa Pharmaceuticals.

“It is the right time to have an excellent fully integrated, patient-focused biotechnology organization like PTC Therapeutics take over the late-stage development of CNSA-001 so that this promising compound becomes available to patients in the near future.”