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Merrimack Aims For Penny-Wise Pipeline of Cancer Drugs

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spun out Silver Creek Pharmaceuticals, for example, solely so its platform could be used to create cardiovascular drugs. And Mulroy says if other in-house ideas in neurology, infectious disease, bone and joint disease reach the proof of concept stage as well, Merrimack will spin those out too.

Merrimack currently has six cancer drug candidates in clinical trials, and a pipeline of other molecules coming behind all of that, Mulroy says. The breadth of opportunity is what drove Merrimack’s decision to go public in March 2012. It had four drugs in the clinic at the time and more coming, and needed more cash to keep all of its programs going. By the time it filed its initial IPO prospectus, Merrimack said it had already burned through more than $285 million of investor money over 11 years. The company’s venture backers surely were ready to start realizing some returns on that investment.

But all of that investment, in time and money, won’t mean a thing to public investors unless Merrimack shows hard clinical evidence that its approach produces drugs that really work.

Merrimack will get a big chance to prove itself shortly when it finishes several mid-stage tests of MM-121, a cancer antibody targeting HER-3, or ErbB-3, a receptor on the surface of cancer cells.

Merrimack is going after the HER-3 because its computer models showed that the protein binded to other receptors in the same family such as HER-1 or HER-2 (targets of other successful cancer drugs like trustuzumab (Herceptin) and then amplifies their signal. So in theory, targeting HER-3 should be a more effective way to fight tumors. Merrimack created MM-121 based on its computer models, and became quickly encouraged when it put the drug into early-stage trials. In MM-121’s first clinical study, 28 total patients with ovarian or breast cancer got the drug and a chemo agent called paclitaxel. Merrimack targeted patients who had been through several lines of care already, and came back with data showing that 48 percent of patients had a greater than 30 percent reduction in their tumors, according to Mulroy.

Merrimack is now shooting higher, running a series of mid-stage studies with three goals in mind: proving that MM-121 works, that its companion diagnostics can accurately predict who should take it—and who shouldn’t—and using those results to run a more efficient, cheaper late-stage clinical trial.

The studies contain roughly 1,000 combined patients testing MM-121 both as a first- and second-line treatment in ovarian, breast, and lung cancer. Merrimack doesn’t’ expect all of these studies to hit. Rather, it’s using the studies to find out exactly when MM-121 does its best work—before other treatments, after them, or in combination with chemotherapies or other targeted cancer drugs.

Ideally, Merrimack’s diagnostics would successfully pick the patients who subsequently see their tumors shrink and live longer, giving the company the credibility with the FDA to construct a refined, smaller late-stage trial that only includes patients who test positive with its diagnostics. This, in turn, would allow Merrimack to avoid spending the mega-dollars pharmaceutical companies pour into gigantic cancer trials just so they can hopefully enroll enough total patients to find enough who will actually respond to therapy. By keeping the clinical trials small and targeted, Merrimack hopes to save a lot of time and money.

“That’s what we’re trying to get to,” Mulroy says. “We’re trying to drive a stake through the heart of the multi-thousand patient cancer trial. It just needs to be done.”

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