AltruBio, after tweaking checkpoint drug, raises $225M for midphase ulcerative colitis program

AltruBio has roared back after another pivot in its twisty history, securing up to $225 million in series B funding to take an immune checkpoint enhancer through a midphase ulcerative colitis program.

San Francisco-based AltruBio hit reset in 2021. Exiting oncology and prioritizing immunology left the biotech focused on a pipeline led by neihulizumab, an immune checkpoint agonist antibody designed to regulate T-cell homeostasis by targeting PSGL-1. The biotech terminated an ulcerative colitis trial in 2020, citing the pandemic, but was running an acute graft-versus-host disease study at the time of the reset. 

Three years later, AltruBio has moved on from neihulizumab. The biotech remains focused on PSGL-1 but has switched horses, dropping neihulizumab in favor of ALTB-268. The new drug candidate has the same mechanism of action but is “subtly designed as a tetravalent molecule to achieve better efficacy.”

According to AltruBio, the new lead prospect has shown improved potency in down-regulating chronic pathogenic T cells in preclinical and early human tests, raising hopes it can achieve equivalent efficacy to neihulizumab at lower doses. The biotech said the safety profiles are comparable. 

AltruBio put ALTB-268 through a phase 1 study in healthy volunteers in 2023, leading to the initiation of a midphase study in patients with ulcerative colitis who are refractory to biologics. The biotech expects to report data on the primary clinical remission endpoint in the first half of 2025. Beyond that, AltruBio is planning a phase 2b trial that could report data in the second half of 2026.

BVF Partners has signed up to support the program, leading a $225 million series B round that featured assists from new investors RA Capital Management, Cormorant Asset Management and Soleus Capital. Investors that supported AltruBio’s $63 million series A, including the lead aMoon Fund, returned for the latest financing. 

AltruBio’s near-term focus is on ulcerative colitis, but the mechanism is potentially applicable to a range of other diseases. Neihulizumab showed promise in graft-versus-host disease, suggesting that indication is open to ALTB-268, and was studied in psoriatic arthritis and plaque psoriasis earlier in its R&D history.

The breadth of the R&D program reflects the role activated T cells play in various inflammatory diseases. Binding PSGL-1 could down-regulate chronically activated T cells without altering the activity of resting and early-activated T cells. If ALTB-268 can achieve that balance, the molecule could take out the cells that drive multiple inflammatory diseases without diminishing the effectiveness of healthy immune cells.