Novartis announced on Sunday that early data from its experimental actinium-based drug showed signs of anti-tumor activity against prostate cancer, including in patients previously treated with its older drug Pluvicto.
Data from a 101-patient study showed that 52.5% of those previously treated with Pluvicto saw levels of prostate-specific antigen (PSA) fall by at least half when treated with the actinium-based drug. Elevated PSA level is a common marker for prostate cancer.
Response rates were higher in prostate cancer patients who had not received Pluvicto. More than 85% of patients in the trial who had no prior treatment and 58.8% of those who received chemotherapy first had PSA levels fall by half.
TD Cowen analysts said the early data suggest clear efficacy, but cautioned that managing side effects, particularly high rates of dry mouth and severe anemia, will be crucial.
Novartis Chief Medical Officer Shreeram Aradhye said larger trials will be needed to fully assess the severity and reversibility of those side effects, especially if the drug is used in earlier lines of treatment.
The Swiss drugmaker is deepening its bet on radioligand therapies that deliver radiation directly to cancer cells, and is moving ahead with two late-stage studies of the experimental drug. Radioligand therapies now account for nearly 40% of Novartis' cancer R&D investments.
The company already sells Pluvicto and Lutathera, which brought in a combined $2.8 billion last year.
Radiopharma is a fast-growing area of cancer treatment. Eli Lilly, Bristol Myers Squibb, Bayer and AstraZeneca have all acquired radio-drug developers in recent years.
The therapies link a radioactive isotope to a molecule designed to seek out cancer-cell targets. While Pluvicto uses lutetium-177, a beta-emitting isotope, the experimental drug uses actinium-225, an alpha emitter.
"The difference is that much higher amounts of energy (are) delivered across a much smaller distance, and the potential for greater efficacy," Aradhye said.
Some analysts have warned that the current actinium-225 supply is insufficient for growing clinical demand, though newer production efforts could ease constraints.
Aradhye said Novartis is already planning around future isotope needs. In February, the company entered into a long-term supply agreement for actinium with U.S.-based medical isotope producer Niowave.
