Viking hits primary endpoint in phase 2 hip fracture trial

All doses of VK5211 beat placebo in terms of change in lean body mass.

A phase 2 trial of Viking Therapeutics’ VK5211 has hit its primary endpoint. The nonsteroidal selective androgen receptor modulator boosted lean body mass in hip fracture patients, emboldening Viking to look toward a late-phase study.

Investigators enrolled 108 subjects at sites in the U.S. and Eastern Europe and randomized them to receive one of three doses of VK5211 or placebo. The participants were all seniors who were recovering from a hip fracture suffered three to seven weeks earlier. Viking hoped VK5211 would aid patient recovery by triggering testosterone-like gains in muscle and bone tissue without the side effects associated with the hormone.

All doses of VK5211 beat placebo in terms of change in lean body mass. The performance was dose dependent, with the highest dose chalking up the biggest response. Patients in that cohort gained 9.1% more lean body mass than subjects in the placebo group. 

That was a bigger gain than Viking expected to see.

“The observed efficacy exceeded our expectations,” Viking CEO Brian Lian said on a conference call to discuss the clinical data. “The lowest dose performed better than we expected the highest dose to perform.” 

Lian framed a 2% to 3% difference over the control arm as “a very meaningful improvement in lean body mass” on a quarterly results conference call earlier this month. The trial data cleared that bar and also hit the marks Lian provided for functional and other secondary endpoints.

Viking’s functional endpoints, none of which were powered for significance, showed the treatment beat placebo numerically, including “dose-related improvements” in the six-minute walk test. 

Lian had primed investors over the preceding quarters to see that as the hoped-for outcome. In a longer, powered study, the expectation is that gains in body mass seen in the phase 2 will translate into statistically significant improvements against functional measures. That theory will be put to the test down the line. 

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While Viking is going into talks with the FDA about the design of the phase 3 trial assuming lean body mass won’t be acceptable as a regulatory endpoint, the six-minute walk test, short physical performance battery and other functional measures accepted by the FDA in other pivotal studies may take center stage. 

Viking is gearing up for the regulatory discussions by continuing to sift through its data. At some point soon, Viking will also need to tap investors for more cash. The biotech closed out the last quarter with less than $10 million in cash, equivalents and investments. 

The phase 2 data provide a fundraising opportunity, although the results only gave Viking—which has a sub-$100 million market cap—a modest, single-digit stock bump. Viking has seen its stock slide more than 66% since it went public, over which time it pushed back the forecast completion of the VK5211 study from the pre-IPO target of the first half of 2016.