Homology Medicines, Inc. announced that the U.S. Food and Drug Administration (FDA) lifted the clinical hold previously placed on the pheNIX gene therapy clinical trial with investigational HMI-102 for adults with phenylketonuria (PKU). The FDA noted in its response that Homology satisfactorily addressed all clinical hold issues identified in its letter of March 17, 2022. Homology plans to share the changes to the protocol, which include a new steroid-sparing immunosuppression regimen that incorporates a T-cell inhibitor and a shorter course of steroids, with the clinical trial sites.

As previously disclosed, the clinical hold on the pheNIX trial pertained to elevated liver function tests observed in the trial, which were all resolved with no hospitalizations required. Homology's response to the FDA included changes to the protocol intended to enhance risk-mitigation measures and a new immunosuppression regimen with the T-cell inhibitor tacrolimus, which will be used in combination with a reduced duration of prophylactic steroids. The same approach is being used in Homology's ongoing pheEDIT gene editing trial for PKU and juMPStart gene therapy trial for Hunter syndrome.

Similar regimens have been shown to dampen the immune response to AAVs in the clinical setting.