# RayzeBio
RayzeBio, Inc. was a San Diego-based clinical-stage radiopharmaceutical company, founded in 2020, that developed [Actinium-225](https://www.edgepedia.org/actinium-225) drug conjugates for solid tumor cancers; it went public on Nasdaq in September 2023 and was acquired by [Bristol Myers Squibb](https://www.edgepedia.org/bristol-myers-squibb) (BMS) in February 2024, after which it operated as a wholly owned BMS subsidiary.[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) • [2](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium)
| Key fact | Detail |
| --- | --- |
| Founded | Began operations August 2020, San Diego, California[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) |
| Sector | Biotechnology; targeted radiopharmaceutical therapeutics[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) |
| Chief executive | Ken Song, M.D.[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) |
| Private capital raised | $418 million per the company's IPO prospectus; $396.4 million per its SEC Form D filings[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) • [4](https://www.sec.gov/Archives/edgar/data/1825367/000182536720000002/) |
| IPO | Upsized $358 million offering at $18.00 per share, trading as RYZB from September 15, 2023[5](https://www.businesswire.com/news/home/20230919072519/en/RayzeBio-Inc.-Announces-Closing-of-Upsized-%24358-Million-Initial-Public-Offering-and-Full-Exercise-of-Underwriters-Option-to-Purchase-Additional-Shares) |
| Lead candidate | RYZ101 (225Ac-DOTATATE), Phase 3 in GEP-NETs[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) |
| Outcome | Acquired by Bristol Myers Squibb for $62.50 per share (about $4.1 billion equity value), completed February 26, 2024[6](https://www.bms.com/assets/bms/us/en-us/pdf/investor-info/2023/bms-ryzb-press-release.pdf) • [2](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium) |
## Founding and people
RayzeBio began operations in August 2020 and described itself as a vertically integrated radiopharmaceutical therapeutics company, meaning it handled discovery, manufacturing, and clinical development in-house rather than outsourcing.[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) Its president and chief executive was Ken Song, M.D., a career entrepreneur who previously co-founded and led Ariosa Diagnostics (acquired by Roche), served as chief executive of [Metacrine](https://www.edgepedia.org/metacrine), and was executive chairman of [Omniome](https://www.edgepedia.org/omniome) (acquired by [Pacific Biosciences](https://www.edgepedia.org/pacific-biosciences)).[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) The leadership team at the time of its 2023 stock registration included chief medical officer Susan Moran and chief financial officer Arvind Kush.[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm)
The company's private backers included venBio Partners, Venrock Healthcare Capital Partners, Versant Ventures, and [Viking Global Investors](https://www.edgepedia.org/viking-global-investors).[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm)
## Technology and pipeline
**Actinium-225 drug conjugates** pair a peptide that binds a tumor marker with the alpha-emitting isotope Actinium-225. RYZ101, the lead candidate, consists of DOTATATE, a peptide binder, and a chelator bound to Ac225, designed to deliver the isotope to tumors overexpressing the somatostatin receptor 2 (SSTR2), which is common in gastroenteropancreatic neuroendocrine tumors (GEP-NETs).[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm) Alpha particles deliver up to 400 times higher energy than beta particles, causing double-stranded DNA breaks that are lethal to cancer cells.[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) The company reported having conducted over 500 in-vivo experiments with Ac225 and operated a 28,000-square-foot radiopharmaceutical R&D facility alongside a 63,000-square-foot GMP manufacturing facility expected to be operational by the end of 2023.[1](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm)
By June 30, 2023, 17 patients had completed RYZ101 dosing in early testing: six had partial responses and five had confirmed partial responses, a confirmed objective response rate of 29% by RECIST v1.1.[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) The company was enrolling a registrational Phase 3 trial, ACTION-1, in GEP-NET patients who had progressed after lutetium-177 (Lu177) therapy, comparing RYZ101 against everolimus, sunitinib, or high-dose somatostatin analogs, and was also running a Phase 1b trial in extensive-stage small cell lung cancer (ES-SCLC) and developing RYZ801, a glypican-3-targeting program for hepatocellular carcinoma, plus a CA9-targeting asset for renal cell cancer.[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) • [6](https://www.bms.com/assets/bms/us/en-us/pdf/investor-info/2023/bms-ryzb-press-release.pdf)
## Funding and IPO
Before going public, RayzeBio raised $418 million in equity capital, according to its IPO prospectus, while its SEC Form D filings record $396,432,007 as the total amount sold across those offerings.[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) • [4](https://www.sec.gov/Archives/edgar/data/1825367/000182536720000002/) Round-by-round amounts and valuations are not established in the sourced record.
The IPO was upsized and closed at $358 million total: RayzeBio sold 18,706,240 shares and a selling stockholder sold 1,163,000 shares at $18.00 per share, with gross proceeds to the company of approximately $336.7 million.[5](https://www.businesswire.com/news/home/20230919072519/en/RayzeBio-Inc.-Announces-Closing-of-Upsized-%24358-Million-Initial-Public-Offering-and-Full-Exercise-of-Underwriters-Option-to-Purchase-Additional-Shares) (By contrast, the 424B4 pricing table shows $310,996,800 in initial gross proceeds before the underwriters' option was exercised in full.)[3](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm) The shares began trading on the Nasdaq Global Market on September 15, 2023 under the symbol RYZB.[5](https://www.businesswire.com/news/home/20230919072519/en/RayzeBio-Inc.-Announces-Closing-of-Upsized-%24358-Million-Initial-Public-Offering-and-Full-Exercise-of-Underwriters-Option-to-Purchase-Additional-Shares)
## Acquisition by Bristol Myers Squibb
On December 26, 2023, less than four months after the IPO, BMS agreed to acquire RayzeBio for $62.50 per share in cash, a total equity value of approximately $4.1 billion, or $3.6 billion net of estimated cash acquired; both boards approved unanimously.[6](https://www.bms.com/assets/bms/us/en-us/pdf/investor-info/2023/bms-ryzb-press-release.pdf) The offer was roughly 3.5 times the $18.00 IPO price.[5](https://www.businesswire.com/news/home/20230919072519/en/RayzeBio-Inc.-Announces-Closing-of-Upsized-%24358-Million-Initial-Public-Offering-and-Full-Exercise-of-Underwriters-Option-to-Purchase-Additional-Shares) • [6](https://www.bms.com/assets/bms/us/en-us/pdf/investor-info/2023/bms-ryzb-press-release.pdf) Reuters framed the deal as BMS's second multi-billion-dollar cancer acquisition in that period and part of a broader wave of radiopharmaceutical deals by large pharmaceutical companies.[7](https://www.reuters.com/markets/deals/bristol-myers-buy-rayzebio-about-41-billion-2023-12-26/)
The tender offer expired one minute after 11:59 p.m. ET on February 22, 2024, with approximately 53,052,499 shares, about 86% of outstanding shares, validly tendered. The merger closed on February 26, 2024 under Delaware General Corporation Law Section 251(h), RayzeBio became a wholly owned BMS subsidiary, and its shares ceased trading on Nasdaq.[2](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium)
## Recent developments
After the acquisition, RayzeBio continued to operate as a San Diego-based biotech with BMS's backing, and the Phase 3 trial in SSTR-positive GEP-NET patients previously treated with lutetium-177 therapies and the Phase 1b trial in first-line ES-SCLC remained in enrollment.[2](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium) • [8](https://rayzebio.com/about/about-overview/) The deal included a radiopharmaceutical manufacturing facility expected to begin operating in the first half of 2024.[2](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium)
BMS has since opened a 77,000-square-foot RayzeBio manufacturing facility in [Indianapolis](https://www.edgepedia.org/indianapolis), Indiana, now fully operational for clinical orders and manufacturing clinical doses of RYZ101.[9](https://www.bms.com/life-and-science/insights/new-rayzebio-hub-accelerates-next-gen-cancer-therapies.html) The facility offers on-demand manufacturing with delivery to a patient's treatment facility within three days of release and can deliver tens of thousands of doses annually at capacity; BMS notes approximately 200,000 patients in the United States live with GEP-NETs.[9](https://www.bms.com/life-and-science/insights/new-rayzebio-hub-accelerates-next-gen-cancer-therapies.html)
## References
1. [RayzeBio, Inc. Form S-1 (SEC EDGAR, 2023)](https://www.sec.gov/Archives/edgar/data/1825367/000119312523220093/d492091ds1.htm)
2. [Bristol Myers Squibb Completes Acquisition of RayzeBio (Business Wire via Nasdaq, 26 Feb 2024)](https://www.nasdaq.com/press-release/bristol-myers-squibb-completes-acquisition-of-rayzebio-adding-differentiated-actinium)
3. [RayzeBio Form 424B4 IPO prospectus (September 2023)](https://www.sec.gov/Archives/edgar/data/1825367/000119312523237010/d492091d424b4.htm)
4. [RayzeBio Form D filing (SEC EDGAR)](https://www.sec.gov/Archives/edgar/data/1825367/000182536720000002/)
5. [RayzeBio Announces Closing of Upsized $358 Million IPO (Business Wire, Sep 19, 2023)](https://www.businesswire.com/news/home/20230919072519/en/RayzeBio-Inc.-Announces-Closing-of-Upsized-%24358-Million-Initial-Public-Offering-and-Full-Exercise-of-Underwriters-Option-to-Purchase-Additional-Shares)
6. [Bristol Myers Squibb Adds Premier Radiopharmaceutical Platform with Acquisition of RayzeBio (press release, 26 Dec 2023)](https://www.bms.com/assets/bms/us/en-us/pdf/investor-info/2023/bms-ryzb-press-release.pdf)
7. [Bristol Myers to buy RayzeBio for $4.1 billion in targeted cancer therapy push (Reuters, 26 Dec 2023)](https://www.reuters.com/markets/deals/bristol-myers-buy-rayzebio-about-41-billion-2023-12-26/)
8. [About RayzeBio (company site)](https://rayzebio.com/about/about-overview/)
9. [New RayzeBio hub accelerates next-gen cancer therapies (BMS newsroom)](https://www.bms.com/life-and-science/insights/new-rayzebio-hub-accelerates-next-gen-cancer-therapies.html)
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*Initially written Sep 17, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 25, 2026*
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