Cellectar Biosciences Announces Strategic Supply Agreement with Ionetix for Actinium-225 and Astatine-211 to Advance Targeted Alpha Therapies

Rhea-AI Summary

Cellectar Biosciences (NASDAQ: CLRB) announced a multi-year supply agreement with Ionetix to secure clinical- and commercial-scale cGMP-grade Actinium-225 (Ac-225) and Astatine-211 (At-211) for development of targeted alpha therapies, including the phospholipid radioconjugate CLR-225 for solid tumors.

Ionetix will install a second cyclotron at its Michigan facility, with one cyclotron dedicated to Ac-225 and the other to At-211, aiming to provide a dependable, scalable isotope supply for clinical trials and potential commercial launches.

Positive

• Multi-year supply agreement secured for Ac-225 and At-211
• Ionetix adding second cyclotron to enable dedicated Ac-225 and At-211 production
• Supply covers clinical and commercial scale to support CLR-225 development

Negative

• Single-supplier dependency for clinical and potential commercial isotope supply
• No quantities, pricing, or delivery timetable disclosed in the agreement

Key Figures

Critical radioisotopes 2 alpha-emitting isotopes Actinium-225 and Astatine-211 named in the supply agreement

Cyclotrons on-site 2 cyclotrons Ionetix Michigan facility housing two cyclotrons for Ac-225 and At-211

Market Reality Check

$3.18 Last Close

Volume Volume 50,167 is slightly below the 20-day average of 53,659 (relative volume 0.93). normal

Technical Shares at $3.20 are trading below the 200-day moving average of $6.38 and 84.46% below the 52-week high of $20.59.

Peers on Argus 1 Up

CLRB fell 11.6% while peers showed mixed moves: EDSA -13.61%, PULM -8.03%, THAR -2.44%, SYBX -1.87%, and LSTA up 3.55%. Momentum scanner only flagged biotech peer GOVX up 4.62% without news, suggesting today’s CLRB move was stock-specific rather than a broad sector rotation.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Nov 13	Earnings and update	Negative	-18.0%	Q3 2025 results with clinical updates and highlighted liquidity risk.
Nov 06	Earnings call notice	Neutral	+2.7%	Announcement of upcoming Q3 2025 results call and webcast.
Oct 27	Regulatory designation	Positive	-10.3%	FDA Rare Pediatric Disease Designation for iopofosine I 131 in r/r pHGG.
Oct 14	Preclinical data	Positive	+1.6%	Promising preclinical CLR 225 data in pancreatic cancer models.
Oct 07	Financing and warrants	Negative	-16.9%	Agreements to raise $5.8M via warrant exercises and new warrants.

Pattern Detected

Across the last five news events, CLRB often showed sharp negative reactions to financings and even some positive regulatory or clinical milestones, with only one clear divergence where good news was met by a selloff.

Recent Company History

Over the past few months, Cellectar reported Q3 2025 results on Nov 13 with clinical and regulatory progress but also liquidity concerns, and the stock fell 18%. A rare pediatric disease designation on Oct 27 led to a 10.25% drop, while promising preclinical CLR-225 data on Oct 14 produced a modest 1.64% gain. Financing activity on Oct 7 to raise $5.8M triggered a 16.86% decline. Today’s supply agreement further advances the CLR-225 and alpha-therapy strategy built in these prior updates.

Market Pulse Summary

This announcement expands Cellectar’s targeted alpha therapy capabilities by securing multi-year cGMP-grade Actinium-225 and Astatine-211 supply for CLR-225 and other programs. It builds on earlier preclinical CLR-225 data and recent regulatory milestones, while prior filings note liquidity and going-concern risks. Investors may watch future clinical trial initiations, additional partnership activity, and funding developments as the company works toward potential commercialization of its radiotherapeutic pipeline.

Key Terms

actinium-225 medical

"for two critical alpha-emitting radioisotopes: Actinium-225 (Ac-225) and Astatine-211"

Actinium-225 is a rare, radioactive form of the metal actinium used as a microscopic radiation source in some cancer treatments; it emits very strong, short-range radiation that can destroy diseased cells when attached to a carrier drug. Investors pay attention because supply is limited and production is complex, so shortages or cost changes can directly affect the development, manufacturing and valuation of companies pursuing therapies that rely on this scarce medical “fuel.”

targeted alpha therapy medical

"into potential commercial launches of targeted alpha therapy (TAT) candidates."

A cancer treatment that attaches tiny, highly energetic bits of radiation called alpha particles to a molecule that seeks out tumor cells, delivering a powerful, localized dose much like a guided missile hitting only its target. Investors care because it can offer strong anti-tumor effects with fewer whole-body side effects than traditional radiation, creating significant commercial upside, clinical and regulatory risks, and clear milestones that affect company value.

cyclotron technical

"Ionetix Corporation, a leading cyclotron technology innovator and full-service"

A cyclotron is a machine that uses electromagnetic fields to speed up charged particles in a spiral path, producing radioactive isotopes or particle beams used in medical imaging, cancer treatments and research. For investors it matters because cyclotrons act like specialized factories that create short‑lived, high‑value medical ingredients: access to or ownership of a cyclotron can affect supply reliability, regulatory approvals, treatment availability, revenue potential and capital or operating costs.

AI-generated analysis. Not financial advice.

Supports Development of Phospholipid Radioconjugate (PRC) CLR-225 for the Treatment of Solid Tumors

FLORHAM PARK, N.J. and LANSING, Mich., Dec. 16, 2025 (GLOBE NEWSWIRE) -- Cellectar Biosciences, Inc. (NASDAQ: CLRB), a late-stage clinical biopharmaceutical company focused on the discovery and development of drugs for the treatment of cancer, today announced a multi-year supply agreement with Ionetix Corporation, a leading cyclotron technology innovator and full-service radioisotope manufacturer, for two critical alpha-emitting radioisotopes: Actinium-225 (Ac-225) and Astatine-211 (At-211).

Under the agreement, Ionetix will provide Cellectar with a reliable, clinical and commercial-scale supply of cGMP-grade Ac-225 and At-211 to support its drug development programs through clinical trials and into potential commercial launches of targeted alpha therapy (TAT) candidates.

“As we prepare for the future expansion of Cellectar’s radiotherapeutic pipeline beyond our beta and Auger emitter clinical programs and work to advance CLR-225 into clinical trials as a potential treatment for challenging solid tumor cancers such as pancreatic cancer, establishing a dependable and fully scalable supply of high-quality alpha-emitting isotopes is essential for the development of our targeted PRC pipeline,” said Jarrod Longcor, chief operating officer of Cellectar Biosciences. “This collaboration with Ionetix ensures sufficient supply of these isotopes moving forward.”

Cellectar’s proprietary phospholipid ether platform technology has demonstrated robust delivery of a wide variety of isotopes directly to tumor cells for a broad range of cancers. This unique capability allows Cellectar to identify the optimal isotope for the targeted tumor type. When paired with the platform, Ac-225 and At-211 are ideal alpha-emitting radioisotopes designed to deposit highly localized, high-energy radiation, that can destroy tumors while sparing surrounding healthy tissue.

“We are excited to collaborate with Cellectar to support their mission to deliver life-extending therapies for cancer patients,” said David Eve, vice president of medical affairs at Ionetix. “We are currently installing a second cyclotron at our Michigan facility, which will now house two cyclotrons on-site—one dedicated to commercial-scale Ac-225 production and the other dedicated for At-211 production. Our cyclotron-based platform is designed to meet the growing demand for Ac-225 and the rapidly emerging need for At-211—both essential to advancing Cellectar’s next-generation TATs.”

About Cellectar Biosciences, Inc.

Cellectar Biosciences is a late-stage clinical radiopharmaceutical company focused on the discovery and development of proprietary drugs for the treatment of cancer. The company’s core objective is to leverage its proprietary Phospholipid Drug Conjugate™ (PDC) delivery platform to develop the next-generation of cancer cell-targeting treatments that deliver improved efficacy and better safety.

For more information, please visit www.cellectar.com or join the conversation by liking and following us on the company’s social media channels: X, LinkedIn, and Facebook.

Forward-Looking Statements

This news release contains forward-looking statements. You can identify these statements by our use of words such as “may,” “expect,” “believe,” “anticipate,” “intend,” “could,” “estimate,” “continue,” “plans,” or their negatives or cognates. These statements are only estimates and predictions and are subject to known and unknown risks and uncertainties that may cause actual future experience and results to differ materially from the statements made. These statements are based on our current beliefs and expectations as to such future outcomes. Drug discovery and development involve a high degree of risk. Factors that might cause such a material difference include, among others, uncertainties related to the ability to identify suitable collaborators, partners, licensees or purchasers for our product candidates and, if we are able to do so, to enter into binding agreements with regard to any of the foregoing, or to raise additional capital to support our operations, or our ability to fund our operations if we are unsuccessful with any of the foregoing. A complete description of risks and uncertainties related to our business is contained in our periodic reports filed with the Securities and Exchange Commission including our Form 10-K for the year ended December 31, 2024, and our Form 10-Q for the quarterly period ended September 30, 2025. These forward-looking statements are made only as of the date hereof, and we disclaim any obligation to update any such forward-looking statements.

Media/Investor Contacts:

For Cellectar Biosciences:

Anne Marie Fields
Precision AQ
212-362-1200
Annemarie.fields@precisionaq.com

For Ionetix:

David Eve
VP, Medical Affairs
812-972-0673
deve@ionetix.com

FAQ

What did Cellectar (CLRB) announce on December 16, 2025 about Ac-225 and At-211 supply?

Cellectar announced a multi-year agreement with Ionetix to supply cGMP-grade Ac-225 and At-211 for clinical and commercial use.

How does the Ionetix deal affect Cellectar's CLR-225 development timeline?

The agreement is intended to provide a dependable, scalable isotope supply to support advancing CLR-225 into clinical trials and potential commercial launches.

Will Ionetix increase production capacity for CLRB isotopes?

Yes; Ionetix is installing a second cyclotron at its Michigan facility, with one cyclotron dedicated to Ac-225 and the other to At-211.

Does the announcement disclose volumes, pricing, or delivery schedules for CLRB isotopes?

No; the press release does not disclose specific volumes, pricing, or delivery timetables.

What risk does the Ionetix supply agreement create for CLRB shareholders?

The company will rely on a single named supplier for clinical and commercial-scale Ac-225 and At-211, creating supplier concentration risk.

Are Ac-225 and At-211 intended for use with Cellectar's phospholipid platform for solid tumors?

Yes; the isotopes are intended to be paired with Cellectar's phospholipid ether platform to develop targeted alpha therapies such as CLR-225 for solid tumors.