Unum, Homology Plan IPOs, as Unum Reveals Two Patient Deaths

Xconomy Boston — 

Two Boston-area biotech startups are shrugging off the recent stock market volatility as they press forward with plans for initial public stock offerings. Genetic therapies company Homology Medicines and cell therapy developer Unum Therapeutics each filed IPO paperwork with regulators late Friday. Unum’s filing revealed that two patients died in a Phase 1 trial late last year. The FDA placed a hold on the trial in December and lifted it last month.

Homology set a preliminary goal of raising $100 million. The Bedford, MA, company has applied for a listing on the Nasdaq Global Market under the stock symbol “FIXX.” Unum, based in Cambridge, MA, set an initial $86 million IPO target. The company has applied for a Nasdaq listing under the symbol “UNUM.”

Unum develops cell therapies that involve extracting a patient’s T cells, engineering them to be better cancer fighters, and then infusing them back into the patient. Novartis (NYSE: NVS) and Gilead Sciences (NASDAQ: GILD) were the first to win FDA approval for similar drugs, called CAR-T therapies, in tough-to-treat blood cancers. Unum is trying to target a broader range of cancers. It engineers its T cells with a surface protein meant to latch on to a wide range of antibodies. The approach could expand this type of cancer therapy to solid tumors, which so far have been challenging to treat with antibody drugs. But Unum’s filings have revealed clinical trial developments that may worry investors.

An early look at Phase 1 data for the drug ACT087 in non-Hodgkin lymphoma showed that two patients died, according to Unum’s filing. One of those deaths was considered to be related to the Unum drug. Severe side effects, including an immune system reaction called cytokine release syndrome, were also observed in other patients.

The FDA halted Unum’s study in December to investigate, according to the filing. Unum said that clinical hold was lifted in February after the regulator reviewed more information from the study. Clinical testing of ACT087 has resumed, and Unum says it has made changes to the study and the dosing of its drug. The company also says it expects these changes will reduce side effects, and make them easier to manage when they occur.

In addition to working on cell therapies on its own, Unum has a collaboration with Bothell, WA-based Seattle Genetics (NASDAQ: SGEN). That work is still preclinical. As of Dec. 31, Unum reported having $40.9 million in cash.

Meanwhile, Homology plans to use proceeds from its IPO to start clinical trials testing its treatments for genetic disorders. The company is developing treatments that are based in gene editing, as well as gene therapy. Homology calls its therapies “genetic medicines.” Its gene-correction technology replaces a defective gene with a functioning version, the company says in its filing. Homology also says it can repair genetic mutations in a targeted way that avoids making unwanted genetic changes.

Homology delivers its genetic medicines using an adeno-associated virus (AAV), a modified virus that is a common way to deliver gene therapies. The company says its suite of AAVs can precisely and efficiently deliver genetic therapies—both gene editing and gene therapy treatments—for diseases affecting the liver, central nervous system, bone marrow, lung, and more.

The first disease Homology aims to treat is phenylketonuria (PKU), an inherited disorder that leads to a buildup of an amino acid called phenylalanine. It’s caused by a defect in the gene for an enzyme that breaks down phenylalanine. Homology plans to bring its PKU gene therapy candidate, HMI-102, into a Phase 1/2 study. The company expects to identify a second therapeutic candidate for the disease, one developed using its gene editing technology, later this year.

Homology’s most recent funding round, an $83.5 million Series B financing, closed last August. As of Dec. 31, the company reported having $129.6 million in cash.

Photo by Wade Roush.