Dartmouth biotech company IMV on Tuesday revealed “breakthrough” results in the Phase 2 clinical trials of its flagship drug DPX-Survivac, which sparked a sell-off of its shares that was as puzzling as it was dramatic.

IMV, which specializes in using a person’s immune system to battle such diseases as cancer, announced an update on DPX-Survivac, saying the study of 22 patients with advanced recurrent ovarian cancer marked a “pivotal milestone” for the company.

The study was able to draw data from 19 patients, and 15 of them, or 79 percent, “achieved disease control". Also, 10 of them, or 53 percent, experienced a shrinkage of their tumours. Seven patients, or 37 percent, showed benefits lasting at least six months.

The statement also said that IMV plans to meet soon with the Food and Drug Administration in the U.S. to discuss the results as it continues with other trials of DPX-Survivac in partnership with the multi-national pharma company Merck & Co. IMV believes the results are strong enough to merit an accelerated pathway for the drug.

“Today’s update marks a pivotal milestone for IMV and, we believe, is a breakthrough for targeted T cell immunotherapies, as these results demonstrate for the first time activity in a solid tumor, which is among the hardest to treat,” said CEO Frederic Ors in the statement.

“Notably, these results also continue to validate the unique mechanism of our DPX platform and the relevance of survivin as a cancer target, as we await updated Phase 2 data from two additional studies of DPX-Survivac in the first half of this year.”

Investors were decidedly less enthusiastic, as IMV shares in Toronto and New York lost about 40 percent of their value on Tuesday. The shares on Nasdaq fell US$1.91 or 40 percent to US$2.87, their lowest level since November. It should be noted that IMV shares, like those of most clinical phase biotech companies, are notoriously volatile.

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Developed from a Dalhousie University experiment to deliver birth control to seals on Sable Island, DPX-Survivac uses the body’s immune system to battle diseases by delivering doses of medication over a prolonged period. Survivac locates Survivin, a substance found in the outer layer of cancer tumors, then attacks the tumors repeatedly.

The most important trials are those into the drugs' impact on ovarian cancer, an especially lethal affliction. Ors told Entrevestor in a September interview the company hopes the drug will be effective in prolonging the lives of people suffering with hard-to-treat forms of cancer.

IMV raised $29.5 million in March 2019 by selling shares to investors, and Ors said late last year IMV had enough capital to last through 2020. In the next nine months or so, it has to decide how to proceed with bringing DPX-Survivac to market – either on its own (which would require more capital), with a partner or by selling the drug or the whole company.

In the statement on Tuesday, Ors said the latest study shows DPX-Survivac was “active, durable and well-tolerated in advanced ovarian cancer.”

The company’s Chief Medical Officer Joanne Schindler said the findings are significant because these patients had already tried other treatments and had few options other than single-agent chemotherapy, which generates responses in only 12 percent of patients.

“These results demonstrate DPX-Survivac’s clinical potential as a well-tolerated and, possibly, more effective treatment than currently available therapies,” she said. “We believe this outcome places DPX-Survivac at the forefront of a new paradigm in the treatment of ovarian cancer and other solid tumors, as a targeted T cell therapy that can achieve durable responses while maintaining quality of life.”