Merrimack hoping for first product approval this year

The US FDA has accepted Merrimack's rolling application to market its first product, the second-line pancreatic cancer therapy MM-398, setting it on course for possible approval later this year.

The filing is based on phase III data in metastatic pancreatic cancer in patients who have received prior treatment with gemcitabine which showed an increase in overall survival (OS) when it was added onto 5-fluorouracil (5-FU) and leucovorin, prompting the company to ask the FDA for a priority review.

The trial – called NAPOLI-1 – was the first phase III study in a post-gemcitabine setting to show a survival benefit in this aggressive form of cancer, according to Merrimack's chief executive Robert Mulroy.

MM-398 is a liposomal formulation of the older chemotherapy drug irinotecan, which is known to be effective in pancreatic cancer but is limited by serious side effects. The formulation helps usher the active drug into the tumour and prolongs its cancer cell-killing effects and reduces systemic toxicity.

Merrimack's drug targets a patient group with limited therapeutic options and in NAPOLI-1 boosted survival from around four to six months.

On the strength of the data Merrimack licensed rights to the drug outside the US and Taiwan to Baxter last year in a deal valued at up to $970 million, including $100 million upfront, that Mulroy said recently would also "drive the expansion of MM-398 into multiple additional cancer indications."

At the time questions were raised about the rationale of the deal – particularly in light of competing therapies such as Celgene's Abraxane (albumin bound paclitaxel) – so the FDA's acceptance of the rolling application is a boost to both companies.

Analysts have suggested that MM-398 could become a $500 million-plus product at peak, assuming a per-patient treatment cost of around $80,000, and that it now has a strong chance of being approved.

Merrimack plans to start trials of the drug in first-line pancreatic cancer as well as gastric cancer later this year.

Meanwhile, following behind MM-398 is MM-121, a drug in trials for breast, ovarian and lung cancers characterised by ErbB3 mutations that was partnered with Sanofi last October in a $530 million deal, including $60 million upfront.

The company also recently started phase II trials of M-302, an HER2-targeted nanoliposomal encapsulation of doxorubicin, in metastatic breast cancer that it hopes will also be a candidate for accelerated approval.