Concerns about Obesity Drug Candidates
One of the questions raised during the February Qnexa panel was whether Vivus should conduct a pre- or post-approval cardiovascular (CV) outcomes study. In commenting on the panel outcome, Leerink Swann biotechnology analysts Steven Yoo and Joshua Schimmer, M.D., said that while several members of the panel expressed some concern about the ability to initiate and complete a post-approval CV outcomes study, “we believe that a CV outcomes trial will likely be a requirement for obesity drugs but only as a post-approval commitment.”
Vivus says it designed and developed the drug to decrease appetite and increase satiety. Phase II and III data to date has shown that patients taking Qnexa experienced statistically significant weight loss, glycemic control, and improvement in cardiovascular risk factors when used in combination with a diet and lifestyle modification program.
Qnexa combines two existing drugs, the stimulant phentermine approved for short-term use as a weight loss drug and on the market for about 50 years with topiramate, marketed by Johnson & Johnson for about 16 years as Topamax to treat epilepsy and migraine headache.
Arena’s lorcaserin unlike Qnexa does not combine existing drugs, a company spokesperson pointed out to GEN. It is an NCE thought to act as a selective serotonin 2C receptor agonist. The serotonin 2C receptor is expressed in the brain including the hypothalamus, an area believed to be involved in the control of appetite and metabolism.
Clinical trial results have shown that individuals taking the drug lost 5.8% of their weight after a year compared to 2.5% for those taking a placebo. The difference failed to meet the 5 percentage point criterion set by the FDA. But 47% of those taking lorcaserin lost at least 5% of their weight compared to 22% of those getting a placebo, a result that just exceeded the FDA standard that twice as many people on the drug as on the placebo lose 5% of their weight.
In 2010, the FDA issued a complete response letter (CRL) to Arena for lorcaserin. Nonclinical issues identified by the agency included diagnostic uncertainty in the classification of mammary masses in female rats, unresolved exposure-response relationship for lorcaserin-emergent mammary adenocarcinoma, and unidentified mode of action and unclear safety margin for lorcaserin-emergent brain astrocytoma, the company reported.
With regard to clinical issues, the agency stated that the weight loss efficacy of lorcaserin in overweight and obese individuals without type 2 diabetes was marginal. It recommended that Arena submit the final study report of the trial called BLOOM-DM (behavioral modification and lorcaserin for overweight and obesity management in diabetes mellitus).
Arena resubmitted the NDA last December, and the agency assigned a PDUFA date of June 27. And on March 2 the company announced that it had filed an MAA with the EMA.
Orexigen was the third company to receive a CRL for its anti-obesity candidate, Contrave. The CRL, issued January 31, 2011, noted a single approval deficiency related to cardiovascular safety. The agency asked Orexigen to conduct a randomized, double-blind, placebo-controlled cardiovascular outcomes trial prior to approval.
On February 6, the company said that it reached an agreement with the FDA on an SPA for the outcomes trial. The objective of the study will be to demonstrate that Contrave does not unacceptably increase the risk of major adverse cardiovascular events. The company plans to initiate the Contrave outcomes trial, which will enroll approximately 10,000 patients, late in the second quarter of 2012.
Orexigen’s Contrave is comprised of two existing drugs, the antidepressant Wellbutrin and the addiction drug naltrexone. Naltrexone acts as an opiate antagonist by blocking opioid brain receptors. Bupropion is a norepinephrine-dopamine reuptake inhibitor.