Supernus touts ADHD Phase III data, but results appear to fall short of expectations

CNS-focused Supernus Pharmaceuticals $SUPN reported positive data from keenly watched twin studies testing its non-stimulant ADHD drug in children on Thursday, but the results suggested the treatment does not have a leg up over an existing generic drug on the market.

Shares of the Rockville, Maryland based-company were down about 13% in early trading.

Two doses of the drug SPN-812 were tested against a placebo in each study —  100mg/200mg in study P301, and 200mg/400 mg in study P303.

In the 6-week P301 study, SPN-812 100mg and 200mg had an effect size of 0.54 and 0.57 respectively, the company reported, meeting the main goal of reducing symptoms on an ADHD rating scale. And in the 8-week P303 trial, patients receiving 200mg and 400mg had an effect size of 0.46 and 0.49.

In 2002, Lilly’s $LLY Strattera was the first non-stimulant medication approved for ADHD. It went generic last year and will directly compete against SPN-812 if Supernus’ drug is approved. Strattera achieved an effect size of 0.4-0.6 in trials.

Supernus Chief Jack Khattar reiterated his enthusiasm for the drug on Thursday: “We believe these data from the two pivotal Phase III studies…demonstrate that SPN-812 is a well-differentiated novel non-stimulant treatment option for many children with ADHD.”

Another measure that might help differentiate SPN-812 is onset of action. In study P301, SPN-812 showed a statistically significant improvement over the placebo as early as the first week, a feat the drug was unable to reproduce in study P303.

Despite investor discontent, Cowen’s Ken Cacciatore suggested the data was encouraging: “What the Street appears to be missing today is that parents/caregivers have very limited options in the treatment of ADHD and related behavioral disorders, and therefore there is a real and large need to add to the treatment paradigm,” he wrote.

“SPN-812 compares favorably with market-leading non-stimulant Strattera, but unlike Strattera SPN-812 has a much more rapid onset of action (1 week versus 4-6 weeks), as well as what appears to be a cleaner safety profile. Despite Strattera’s limitations, it reached $535 million in the U.S. before going generic. Additionally, the results compare favorably to Shire’s non-stimulant Intuniv, which within only a few years on the market was on a run-rate of $340 million in sales before it went generic.”

SPN-812 is also being tested in adolescents. One phase III study in this patient population will readout by the end of the year, while another is expected by the first quarter of 2019. The biotech expects to submit a marketing application for the drug in the second half of next year.

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