With fresh $160M, RayzeBio plots sprint through the clinic for lead radiopharmaceutical program — building on Novartis' success
Ever since its launch in 2020, RayzeBio has talked at length about building a platform company to fulfill the potential that radiopharmaceuticals hold — with seven active programs to boast. But it’s stayed mum about what those programs actually are, instead sticking to updates about new funding, hires or partnerships.
That’s by design, according to CEO Ken Song. The former Venrock VC and serial biotech entrepreneur wanted to make sure that he had a real business case before becoming more visible.
“Two years ago, when we were written up, it really was just a couple of us with no lab, no office, and just a nice-looking PowerPoint. And that sort of painted the vision and the plans of what we wanted to do,” Song told Endpoints News. “We’ve now reached a point where the organization is at a place where we do feel that there’s quite a good prospect for the company long term.”
He was exaggerating in a sense — by the time RayzeBio unveiled its $45 million Series A, co-led by Versant and venBio, it already had a set of targets in mind, a deal with PeptiDream to search for peptides and a supply arrangement for Actinium-225.
But now, with more than 200 in vivo studies under its belt, RayzeBio is finally taking the wraps off its lead program as well as a $160 million Series D designed to fund the drug’s dash through the clinic all the way to Phase III.
While RayzeBio set out to discover new peptide binders that will guide cancer-killing radioisotopes to tumor cells, the biotech ultimately settled on a tried-and-true binder for its lead drug, RYZ101.
“I would say at conceptual level, radiopharmaceuticals seem pretty straightforward and easy. You take a binder, a linker, a radioactive isotope, in theory you should have your drug,” Song said.
I would say what we came to fully appreciate is that the discovery process, despite the concept being relatively straightforward and simple, the actual discovery of finding those binders that can have all the right properties to deliver the radioactive isotope is incredibly complex and challenging. And hence, you know, highlighting the fact that we have completed over 200 in vivo studies. We really feel that we needed to generate that amount of experience and data to really understand the basic rules and roadmap in how to discover novel binders against targets of interest to deliver a radioactive isotope.
Novartis uses the same peptide, dotatate, for its approved radioligand therapy Lutathera to treat neuroendocrine tumors, except that it deploys a beta isotope rather than an alpha one. Despite initial dramatic clinical benefit, though, Song noted that patients eventually progress and they have no further options.
That’s where he hopes RYZ101 can come in. By linking dotatate with an alpha isotope dubbed Actinium-225, which he says is 400 to 500 times more powerful than beta isotopes, RayzeBio hopes it can prove itself first in neuroendocrine tumors before moving to a second test in small cell lung cancer.
Thanks to existing clinical data on dotatate-based radiopharmaceuticals, some from academic studies, RayzeBio has designed its first trial such that if the Phase I portion looks good on safety, tolerability and pharmacokinetics, it can move straight into Phase III. Phase I data are expected next year.
The cash infusion, which brings the total haul to $418 million, will also support initial studies of subsequent programs as well as the buildout of an in-house manufacturing facility for commercial-scale production.
While RayzeBio currently works with a contract manufacturer to make its drug material, Song noted the number of companies that can do it is “extremely limited.” Existing radiopharmaceuticals have a shelf life of about three to four days as the radioisotopes decay, and even though RayzeBio stretched that out to five days, the just-in-time nature of the process still adds extra stress.
“We thought that this was a piece that we wanted to have more control and oversight over,” he said.
Viking Global Investors, Sofinnova Investments and Wellington Management co-led the round, joined by existing backers as well as new investors Ally Bridge Group, Sands Capital, Laurion Capital Management and Soleus Capital. An undisclosed global investor also jumped in.