Prima Biomed starts new trials of lead I-O drug but needs more cash, say analysts

Trials in breast cancer and melanoma could help attract a licensing partner.

Prima Biomed has pushed the accelerator on its in-house drug development program, pressing ahead with two trials of its immuno-oncology drug IMP321 in breast and skin cancer.

The Australian biotech—which specializes in drugs that target lymphocyte-activation gene 3 (LAG-3)—has started dosing patients in the second stage of a phase 2b trial of IMP321 in metastatic breast cancer and kicked off an initial combination study with Merck & Co.'s checkpoint inhibitor Keytruda (pembrolizumab) in melanoma.

Analysts at Edison said the developments consolidate Prima Biomed's "leadership" position in LAG-3, but they note the company will need to raise additional cash from a "partnership, milestone payments or alternative forms of funding" to complete the breast cancer trial and advance the drug further.

At the end of 2016 the biotech had around $12 million in cash, but its cash burn is set to increase with the two new trials underway and a top-up may be needed, they suggest.

But with immuno-oncology licensing deals currently running at a premium, the analysts believe Prima Biomed could get $50 million or more upfront from an IMP321 partner, plus generous development and approval milestones.

The breast cancer trial will account for the lion's share of the biotech's increased expenditure this year and should start generating response rate results in the summer, which could help entice a partner. Data on progression-free survival—its primary endpoint—is due in late 2018.

The study is comparing IMP321 to placebo, with both drugs given on top of chemotherapy stalwart paclitaxel, and will test a fivefold higher dose of the immunotherapy than used in an earlier trial which found a 50% overall response rate.

Meanwhile, the combination trial with Keytruda is enrolling patients who do not respond well to three cycles of treatment with Merck's drug and is due to be fully recruited around the middle of 2017, with preliminary data from the first cohort of patients due before year-end.

The rationale for the study is that IMP321 will help initiate an immune response by stimulating antigen-presenting cells, while Keytruda will "release the brakes" on the immune system, enabling a stronger response to the tumor. 

If IMP321 fulfills its early potential, it could be a big product, according to Edison, with peak sales approaching $1 billion in breast cancer and another $480 million on the cards if it proves to be successful as a combination therapy for melanoma.