Hoping to win where Novartis failed, Inhibrx files for $75M IPO

Inhibrx has filed for a $75 million IPO. The Celgene-partnered single-domain antibody specialist will use the money to complete phase 1 trials of three drugs targeting cancers and rare diseases.

California-based Inhibrx is built on a single-domain antibody platform it thinks will yield candidates capable of overcoming limitations that have previously stopped the effective drugging of therapeutic targets.

That belief has led Inhibrx to move two wholly owned cancer programs into the clinic and take a rare disease asset to the cusp of an IND filing. The IPO will support phase 1 trials of these three drugs.

Inhibrx’s clinical-phase assets are INBRX-109 and INBRX-105. INBRX-109 is a tetravalent DR5 agonist designed to improve on the limited efficacy and safety problems that derailed previous attempts to hit the target, such as Novartis’ Ablynx-partnered TAS266. INBRX-105 is a PD-L1 antagonist that also conditionally agonizes 4-1BB in the presence of the immune checkpoint to co-stimulate T cells.

In filing for an IPO now, Inhibrx is asking investors to bet on the candidates before getting a good look at clinical data. Inhibrx has dose escalation data on INBRX-109 that are free from hepatotoxicity, the adverse event that stopped Novartis’ anti-DR5 drug, but won’t have efficacy data until the middle of next year. Dose escalation data on INBRX-105 are due in the second half of 2020.

Inhibrx’s early efforts have attracted the attention of some notable drugmakers. Celgene put Inhibrx on the map in 2013 in a deal that secured it the rights to anti-CD47 antibody INBRX-103, although the prospects of that program took a hit last year when the Big Biotech terminated a phase 1 trial.

More recently, Inhibrx granted Chiesi Farmaceutici the rights to AAT-fusion protein INBRX-101 outside of North America. Chiesi will pay $10 million upfront and buy a $10 million stake in Inhibrx concurrent with the IPO to secure the rights to the rare disease drug.