Karos Reports Positive Safety Data from Phase 1 Trials of PAH Therapy

Karos Pharmaceuticals, a start-up focused on the selective modulation of peripheral serotonin synthesis, recently reported positive results from its Phase 1 clinical trials evaluating KAR5585, a compound being developed to treat orphan diseases such as pulmonary arterial hypertension (PAH) and carcinoid syndrome.

KAR5585 is a first-in-class, selective inhibitor of tryptophan hydroxylase 1 (TPH1), designed to selectively modulate peripheral serotonin (5-HT) biosynthesis, and to reduce disease-related vascular remodeling, vasoconstriction, and inflammation.

Preclinical studies in in vivo models of PAH have shown that KAR5585 can reduce vascular remodeling and occlusions when administered in a dose-dependent manner. The drug can be delivered orally.

Results from the Phase 1 trials in healthy subjects showed that KAR5585 met all expectations in both single and multiple ascending doses, demonstrating its safety, tolerability, and pharmacokinetics profile. The drug induces a dose-dependent reduction in serotonin synthesis.

Pharmacokinetic results support twice a day and, possibly, once a day dosing, and the safety data confirmed the safety profile observed in pre-clinical studies.

Karos anticipates starting a double-blind, randomized Phase 2 trial soon to test the drug as a once daily treatment in PAH patients.

KAR5585 was designated an Orphan Drug for the treatment of PAH by the U.S. Food and Drug Administration (FDA) in October 2015.

Dr. Lewis J. Rubin, an emeritus professor of Medicine at the University of California San Diego and a scientific/clinical advisor to Karos, said in a recent press release: “Despite several available therapeutic options for PAH there remains an unmet need for additional therapies. The data with KAR5585 suggest this compound, targeting a novel pathogenic mechanism, may have the potential to treat PAH and be synergistic with current therapies.”

The company also announced the closing of Series B round of financing, the U.S. issuance of a composition of matter patent for KAR5585, and the appointment of Ed Mascioli, MD, as its chief executive officer.