Pfizer Invests $60 Million in Homology Medicines and Its PKU Gene Therapy Program

Rare Daily Staff

Pfizer has agreed to make a $60 million equity investment in Homology Medicines through the purchase of 5 million shares of Homology common stock at $12 per share.

The investment was made just days after Homology reported positive clinical data from its phase 1/2 trial of HMI-102 gene therapy as a treatment for adults with phenylketonuria (PKU), and plans to move to the expansion phase of the trial.

PKU is a rare inborn error of metabolism caused by a mutation in the PAH gene. PKU results in a loss of function of the enzyme phenylalanine hydroxylase, which is responsible for the metabolism of phenylalanine (Phe), an amino acid obtained exclusively from the diet. If left untreated, toxic levels of Phe can accumulate in the blood and result in progressive and severe neurological impairment. Currently, there are no treatment options for PKU that target the underlying genetic cause of the disease. According to the National PKU Alliance, PKU affects nearly 16,500 people in the U.S. with approximately 350 newborns diagnosed each year. The worldwide prevalence of PKU is estimated to be 50,000 people.

HMI-102 is an experimental gene therapy in clinical development for the treatment of PKU in adults that is designed to encode the PAH gene, which is mutated in people with PKU, delivered via the liver-tropic AAVHSC15 vector. Homology has received Fast Track and Orphan Drug designations for HMI-102 from the U.S. Food and Drug Administration (FDA), and Orphan Drug Designation from the European Medicines Agency (EMA).

The company’s experimental therapy HMI-103 is an experimental, nuclease-free gene editing product candidate in IND-enabling studies for pediatric patients with PKU, whose livers are rapidly dividing. By delivering a functional copy of the PAH gene to replace the mutated copy in the genome, gene editing is the best approach for a potential one-time treatment for this population.

Homology intends to use the net proceeds of the offering to help fund its ongoing and planned PKU clinical trials, as well as the company’s central nervous system programs. Based on current projections, together with the anticipated proceeds of $60 million from the Pfizer equity investment, Homology expects cash resources to fund operations into the third quarter of 2022.

Pfizer’s investment is part of its Breakthrough Growth Initiative, announced in June, to commit up to $500 million to invest in publicly traded companies and help advance their medicines without investing directly in an asset.

The investment expands Pfizer’s growing focus on gene therapies, which includes partnered programs in Duchenne muscular dystrophy, Wilson’s disease, and hemophilia, and the construction of its own manufacturing facilities.

“We believe gene therapy could help provide a potentially transformational therapeutic option for patients living with PKU and is a good strategic fit with our rAAV-associated gene therapy portfolio, said Seng Cheng, senior vice president and chief scientific officer of Pfizer’s Rare Disease Research Unit.

In connection with the investment, Cheng will join Homology’s scientific advisory board to participate in matters related to the development of the company’s PKU product candidates HMI-102 and HMI-103. Homology has granted Pfizer a right of first refusal on future transactions involving these programs.

Photo: Seng Cheng, senior vice president and chief scientific officer of Pfizer’s Rare Disease Research Unit