Current Edition

No return for the Merrimack

  • Merrimack Pharmaceuticals is shelving yet another lead candidate after a review of Phase 1 safety data found the drug wasn’t going to meet an “optimal therapeutic index.”
  • Discontinuing development of the drug, MM-310, leaves Merrimack with essentially just two preclinical immuno-oncology therapies in its pipeline. Given that narrowed focus, the company expects to reduce its workforce through a process similar to past cost-cutting measures. As of Feb. 28, Merrimack had 27 full-time employees, including 16 in R&D.
  • Shares of the Massachusetts-based drugmaker were down more than 20% at Friday’s market open. 

It wasn’t long ago that Merrimack appeared to be a much healthier biopharma.

Toward the end of 2016, the company employed around 400 workers and was starting to see a significant bump in product revenue thanks to its recently launched pancreatic cancer drug, Onivyde (irinotecan).

Pancreatic remains one of the deadliest, most difficult-to-treat types of cancer. Though few therapies have ever made it to market, Onivyde proved an exception. U.S. regulators in late 2015 approved the drug in combination with chemotherapy to treat patients with metastatic adenocarcinoma of the pancreas whose disease progressed following gemcitabine-based therapy.

Merrimack didn’t hold onto the drug for long, however. Debts and cash burn were weighing on the company’s balance sheet, prompting it to lay off the bulk of its workforce and sell Onivyde to France-based Ipsen for $575 million upfront.

At the time, Merrimack said the sale would also help fund pipeline development through 2019. Of particular interest were three experimental cancer therapies: MM-121, MM-310 and MM-141.

That strategy hasn’t panned out as Merrimack hoped, as all three therapies failed in the clinic over the last year. While Merrimack is still testing MM-121 in a couple of cancer types, the company has halted development of MM-141 and is now doing the same with MM-310.

 Credit: Jacob Bell / BioPharma Dive, market data 

Initiatied in February 2017, the Phase 1 study of MM-310 evaluated the drug across a range of solid tumor types. Safety became an issue as the investigation went on, with Merrimack disclosing in November that three patients developed Grade 3 peripheral neuropathy after receiving multiple cycles of MM-310 therapy.

Merrimack tried addressing those safety concerns by amending the study protocol in a few ways, such as making the dosing regimen less frequent. Still, fresh data showed treatment with MM-310 continued to result in significant cumulative peripheral neuropathy — findings that prevent the study from succeeding, according to the company.

“We are disappointed that amending the trial protocol does not appear to have solved the cumulative toxicity observed in patients treated with MM-310,” Sergio Santillana, Merrimack’s chief medical officer, said in an April 4 statement.

As of Dec. 31, Merrimack had $71.3 million in cash, cash equivalents and marketable securities. The company estimates that its financial resources and restructuring efforts will be enough to keep operations going into at least the second half of 2022.

Merrimack spent nearly $66 million in net cash on operational activities last year and recorded a net decrease in cash, cash equivalents and restricted cash of nearly $74 million.

The company said its R&D focus will now be on two preclinical drugs.