US pharmaceutical company Regeneron has signed a strategic agreement with biotech startup Parabilis Medicines (formerly FogPharma) worth up to $2.3 billion. The partners will jointly develop five drugs based on antibody-helix conjugates – a new class of molecules capable of entering cells and blocking proteins that are inaccessible to traditional drugs.
The deal includes an upfront payment of 50million, a 75 million equity purchase in Parabilis, and milestone payments of up to $2.2 billion upon successful completion of studies and drug registration. Additional royalties on future sales and the possibility of expanding the partnership are also included.
The molecules in question are based on helicons – alpha-helical peptides patented by Parabilis. Unlike classical antibodies, which only work with targets on the cell surface, the helixon can cross the lipid membrane into the cell, where it finds and blocks the target protein. This is particularly important for proteins with “flat” surfaces, from which ordinary small molecules simply slip off.
The new agreement comes amid a setback for Regeneron in another promising development. The company earlier reported that a combination of its experimental fianlimab with Libtayo (cemiplimab) failed to show statistically significant benefits in melanoma compared with Keytruda (pembrolizumab) monotherapy. Regeneron thus failed to break into the multibillion‑dollar market for next‑generation checkpoint inhibitors.
The partnership with Parabilis Medicines is Regeneron’s move towards new targeted therapy platforms. Antibody-helix conjugates are seen as a promising approach for diseases where classic methods are powerless, and the deal with the US pharma giant will provide the startup with resources for preclinical and clinical development.
As for Parabilis Medicines, immediately after signing the deal the company said it was targeting a stock market listing. The Massachusetts‑based biotech has not yet disclosed the number of shares it plans to offer or their price. However, in a filing with the US Securities and Exchange Commission on May 19, it stated that the main priority for IPO proceeds would be to launch a Phase III trial of zolucatetid (formerly FOG‑001) – an investigational drug that is a first‑in‑class beta‑catenin inhibitor.
Earlier this year, Parabilis Medicines said it planned to turn the organisation into a “large and meaningful company”. If the IPO goes ahead, Parabilis will join a growing number of biotech companies listing on Nasdaq this year, including Seaport Therapeutics, Hemab Therapeutics, Odyssey Therapeutics and Generate:Biomedicines. In April, Kailera Therapeutics made history with an upsized $625 million IPO – a positive signal that the window for biotech IPOs remains open.
