Ziretaxestat, an oral autotaxin (ATX) inhibitor originated by Galapagos, once garnered excitement as the first molecule to complete a Ph. III clinical program in idiopathic pulmonary fibrosis since the approvals of nintedanib and pirfenidone. Following the disappointing clinical data and discontinuation of the molecule, this annotation revisits ziritaxestat in the context of other inhibitors, recaps the therapeutic hypothesis and how it was discovered, summarizes notable molecular properties for drug discovery scientists, and discusses what happened and what’s next.

RPT193, an oral, second-generation CCR4 inhibitor from RAPT Therapeutics, is in Ph. II clinical trials (400 mg QD) to treat atopic dermatitis (AD) (NCT05399368) and asthma (NCT05935332). CCR4 has been a long outstanding therapeutic target for treating inflammatory diseases, but despite many efforts, no molecule inhibiting this receptor has progressed beyond Ph. I for these indications.

The Shionogi P2X3 ligand-gated ion channel antagonist, sivopixant ( S-600918 ), is an oral Ph. II candidate for refractory chronic cough, which recently completed a its Ph. IIb study, overcoming the projected high dose requirement of a prior preclinical candidate. The molecule has a very polar core structure with both a dioxotriazine and [...]

The ImmunoMet OXPHOS modulator (PC1 inhibitor), IM156 , is a derivative of the long-used biguanide diabetes drug, metformin, that appears to have activity in lung fibrosis models. The therapeutic hypothesis for IPF is that myofibroblasts play an essential role in extracellular matrix remodeling and fibrogenesis that lead to loss of pulmonary [...]

X-165 is an autotaxin inhibitor clinical candidate for idiopathic pulmonary fibrosis discovered using a 3-cycle DEL screen of 225M compounds derived from amide couplings. An unusual spirocyclic amine building block was responsible for most of their non-phosphonate-containing high-enrichment hits. The initially resynthesized hits had [...]