Arcellx raises $85M to take anti-BCMA cell therapy into humans

Arcellx CEO David Hilbert (Arcellx)

Arcellx has raised $85 million to advance cell therapies designed to be safer and more effective than conventional chimeric antigen receptor T-cells (CAR-Ts). The series B will equip Arcellx to move an anti-BCMA candidate into the clinic in multiple myeloma while taking assets against other hematological cancers and solid tumors forward. 

Maryland-based Arcellx is underpinned by technology it thinks can address some of the limitations of first-generation CAR-Ts. Whereas Kite’s Yescarta and Novartis’ Kymriah target tumors using a receptor built into the cell, Arcellx’s candidates lack the means to identify cancer cells. 

Instead, they feature an extracellular domain that binds to a soluble protein targeting mechanism, dubbed sparX, that can be administered separately. The cell therapy’s binding domain connects to the sparX protein, which, in turn, latches onto a tumor target.

The approach is intended to address some of the big limitations of current CAR-Ts. When current CAR-Ts face antigen escape, physicians are unable to adapt the therapy to counter resistance. Using Arcellx’s approach, a physician could administer a sparX for a different target, thereby bypassing the resistance mechanism.

Similarly, a physician could administer two or more monovalent sparX proteins simultaneously to dial up the initial cancer killing power. Arcellx is also working on bispecific and bivalent sparX proteins.

The approach could also improve the safety of cell therapies. Once a conventional CAR-T is in the body, physicians have limited control over the therapy, creating the risk of harmful runaway effects. In theory, Arcellx’s approach should give physicians more control as the power of the therapy is tied to the dose of sparX administered.

Other next-generation cell therapy startups including Autlous, Senti Bio and Unum Therapeutics are trying to achieve similar goals using approaches that both overlap with and diverge from that used by Arcellx.

Investors are betting that Arcellx can differentiate itself from the pack. New investors Aju IB and Quan Capital co-led the series B with the support of other first-time backers of Arcellx. The startup also raised more money from existing investors Novo Holdings, S.R. One Limited, NEA and Takeda Ventures.

Arcellx will use the money to take its anti-BCMA candidate into human testing in the coming months. Given the large number of companies pursuing the same target, the program will provide a tough early test for Arcellx. In parallel, Arcellx will advance an anti-CD123 candidate in acute myeloid leukemia and work on earlier-stage programs in new areas including solid tumors, autoimmune diseases and transplants.