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Analysts: Proteostasis Data Are No Boost vs. Vertex in Cystic Fibrosis

Xconomy Boston — 

As with cancer and HIV infection, progress in treatment for the genetic disorder cystic fibrosis has come with ever-more sophisticated cocktails of drugs.

Proteostasis Therapeutics (NASDAQ: PTI) is one of the firms trying to catch up to cystic fibrosis leader Vertex Pharmaceuticals (NASDAQ: VRTX), but data it reported this morning did not satisfy investors, who sent Proteostasis shares down 61 percent to $1.60 apiece in midday trading.

Boston-based Proteostasis released Monday a panel of data from several Phase 1 studies in CF patients who have a particular genetic profile, a mutation called F508del in the CTFR gene. The results come from three of its own drugs in a single combination, as well as regimens consisting of single Proteostasis drugs added to Vertex’s drugs.

The triple-combination data were closely watched as a potential challenger to Vertex’s franchise, which currently consists of three approved drugs: the monotherapy Kalydeco and the two-drug combinations Orkambi and Symdeko. They generated a combined $3.04 billion in 2018.

Vertex has been developing complex cocktails to reach more people with CF. It plans to pick one of two experimental combinations—both of which had comparable, successful results in Phase 3 testing—to submit for FDA approval later this year. Either of those regimens, if approved, could help Vertex treat up to 90 percent of people with the disease.

So far, Vertex has fended off potential challengers such as Galapagos (NASDAQ: GLPG), whose CF drugs are now in the hands of AbbVie (NYSE: ABBV), and Proteostasis. And the data released from Proteostasis today only appear to have reinforced Vertex’s lead.

Proteostasis’s triple combination—the drugs PTI-428, PTI-801, and PTI-808—would be taken once a day and produced no serious side effects, the company said. Hoping to improve lung strength and reduce chloride in sweat, Proteostasis said patients after 14 days had statistically significant improvements in both measures, and it plans to move into Phase 2 studies this year.

But the layers of data, which also included studies beyond the triple-combination results, did not give investors or analysts confidence that Proteostasis could provide stiff competition to Vertex. Even when Proteostasis filtered out patients whose lungs were predisposed to rapid decline, the remaining patients showed an improvement that was “marginally higher than the results in the total population,” wrote SVB Leerink analyst Geoffrey Porges in a note to investors. “These results fall well short of the… benefit established by Vertex.”

“With some studies still incomplete, several differences in characteristics versus Vertex’s studies, and a number of different doses across the studies, it is difficult to draw definitive conclusions as to whether their combos could be truly competitive with Vertex in the broader market,” wrote RBC Capital Markets analyst Brian Abrahams in a note to investors. “More likely, in our view, the components look like a viable option” to treat patients who aren’t helped by Vertex’s drugs, or as building blocks for combinations using other companies’ products.

Vertex shares, which trade near all-time highs, ticked up slightly to $182.68 apiece in midday trading.

Photo by Hey Paul Studios via Creative Commons.