Agios Pharma has said it will halt clinical development of tebapivat, a PK activator that had reached phase 2 testing in sickle cell disease, after preliminary results proved disappointing. Shares in the company were down almost 18% on the announcement, which said the haemoglobin response rate data observed with tebapivat "were consistent with the class of medicine" but did not establish a "differentiated profile" in SCD. As it turned out, the 12-week phase 2 trial, which compared three doses of tebapivat to placebo, did show improvements in haemoglobin levels and haemolysis. However, the primary endpoint of a haemoglobin response was achieved in 29% to 47% of patients with the PK activator, compared to 33% with placebo. "We look forward to bringing this first-in-class medicine to the sickle cell community and building on the extensive clinical experience generated to date as we work to address the significant unmet need in this debilitating disease," said Sarah Gheuens, Agios' chief medical officer.