A drug developer aiming to create more potent, effective antibodies unveiled a $35 million Series A on Wednesday with the support of the Bill & Melinda Gates Foundation and Canadian VC firm Amplitude Ventures, among other investors.
The startup, Radiant Biotherapeutics, is developing mono-, bi- and trispecific antibodies, CEO Arthur Fratamico said in an interview. The antibodies are manufactured the same way as traditional ones, the CEO said. The company hopes its biologics give the molecules more grips on a target and better potency than traditional antibodies, he added.
The four-year-old Toronto and Philadelphia biotech emerged in April 2023 with an $8 million seed round and is based on work out of the Hospital for Sick Children (SickKids) and the University of Toronto. It now has 14 employees and a pipeline of programs across oncology and infectious diseases, and partnerships with Regeneron and GSK, though Fratamico declined to disclose details of those pacts.
It’s also expanding into inflammatory and immunology indications, Fratamico said. Multiple I&I antibody biotechs have reeled in large financing rounds this year, including Attovia Therapeutics, and a few have been bought out, including Yellow Jersey Therapeutics and Proteologix, among others.
Oncology and HIV plans
Radiant’s lead program is a monospecific antibody that goes after 4-1BB, a co-stimulator that’s key to activating certain cells. The industry’s early approaches in this field in the mid-2000s ran into liver toxicity issues and patient deaths.
Other drugmakers are now taking bispecific approaches, including I-Mab, Johnson & Johnson partner CBMG, Genmab and elsewhere. BioNTech decided not to move forward with Genmab’s PD-L1x4-1BB bispecific last month.
“The other work that people are trying to figure out is, if I take a traditional antibody, can I use a cancer antigen then to help localize or cluster the receptor?” Fratamico said. But that approach comes with challenges, he said.
“The activity, or the clustering, is subject to the density and expression of the tumor antigen, so you get variability from patients or get variability based on the specific cancer. With our approach, we don’t worry about any of that,” Fratamico said. “We just inherently have our 24 Fabs [fragment antigen-binding agents] that cluster and get maximum signal activation. And the goal here is to have single-agent activity.”
The startup is still deciding whether to begin with trials in solid tumors or blood cancers, the CEO said. Radiant is targeting its first clinical test for 2026, he said.
It also has plans in the HIV treatment field. Jean-Philippe Julien’s lab at SickKids is working on HIV programs with the support of the Bill & Melinda Gates Foundation, and Radiant could eventually take them into clinical testing, Fratamico said.
“It’s a highly-mutated virus,” Fratamico said. Whereas with Radiant’s approach, “I hold onto it with a lot of different grips. If I lose one, I’m still holding onto it. I’m clearing virus.”