Arbutus drops development of hep B candidate AB-506

Arbutus Biopharma (Nasdaq: ABUS), a hepatitis B virus (HBV) therapeutic solutions company formerly called Tekmira, yesterday announced its decision to discontinue the clinical development of AB-506, an oral capsid inhibitor. AB-506 was in a Phase Ia/Ib clinical trial for the treatment of chronic hepatitis B (CHB).

News of the decision saw Arbutus’ shares plunge 25.2% to $1.07 in after-hours trading on Thursday.

William Collier, president and chief executive of Arbutus, stated: “We have observed two cases of acute hepatitis in our Phase Ia 28-day clinical trial in healthy volunteers. Consequently, the clinical trial and further development of AB-506 have been stopped.”

“The two subjects are experiencing resolution of their acute hepatitis. We will continue to follow them and the other study participants, as safety is our highest priority at Arbutus,” said Gaston Picchio, chief development officer of Arbutus, adding: “We intend to present results from the AB-506 Phase Ia/Ib clinical trial along with further details regarding the two cases of acute hepatitis at an appropriate scientific meeting later in 2019.”

Michael Sofia, chief scientific officer of Arbutus, added: “While we are disappointed in these recent clinical findings, we have a number of oral follow-on capsid inhibitor compounds with distinct chemical scaffolds that we believe have the potential to contribute to the inhibition of HBV replication as part of a combination regimen. Our objective is to select one of several lead compounds for IND-enabling studies by December of this year.”

As a result of the decision to discontinue further development of AB-506, Arbutus no longer expects to initiate a combination study of AB-506 and AB-729 in the second half of 2020.