2010’s preregistration antiobesity drugs: “That’s all, folks!”

"That's all, folks!" http://bit.ly/gSgL6b

“That’s all, folks!” http://bit.ly/gSgL6b

As we said in our December 8, 2010 blog post, the FDA’s Endocrinologic and Metabolic Drugs Advisory Committee recommended that the FDA approve Orexigen’s Contrave (naltrexone sustained release [SR]/bupropion SR), by a vote of 13-7, for long-term use by certain obese and overweight patients.

This followed the earlier rejections in 2010 by the Advisory Committee and the FDA of two other preregistration antiobesity drugs–Vivus’  Qnexa and Arena Therapeutics’ lorcaserin (Lorqess). Also in 2010, the then-marketed antiobesity drug sibutramine (Abbott’s Meridia) was withdrawn from the market at the FDA’s request. Concern about long-term safety was the major consideration in the rejection of Qnexa and lorcaserin, and safety issues (increased risk of cardiovascular events) were the reason for the withdrawal of sibutramine. Thus the Advisory Committee’s recommendation for approval of Contrave was surprising, to us as well as to many others.

Despite the Advisory Committee’s vote to recommend approval of Contrave, it did have safety concerns. Clinical trials indicate that Contrave treatment can result in elevated blood pressure in some patients. Some panelists were also concerned about the risk of seizures, which have been seen with one of the components of Contrave, bupropion. Especially because of the adverse effect on blood pressure, some panelists expressed concern that Contrave, once approved, might suffer the same fate as sibutramine.

As a result of these safety discussions, the panel voted 11-8 to require Orexigen to conduct a long-term study of the effects of Contrave on cardiovascular health. However, they concluded that that study could be done post-marketing rather than requiring the company to conduct the study in order to gain approval.

Yesterday–January 31, 2011–was the Prescription Drug User Fee Act (PDUFA) deadline for the FDA to act on the approval of Contrave. This morning, Orexigen and its partner for Contrave commercialization, Takeda, announced that the FDA had issued a Complete Response Letter regarding the New Drug Application for Contrave.

The FDA’s Complete Response Letter stated, “before your application can be approved, you must conduct a randomized, double-blind, placebo-controlled trial of sufficient size and duration to demonstrate that the risk of major adverse cardiovascular events in overweight and obese subjects treated with naltrexone/bupropion does not adversely affect the drug’s benefit-risk profile.”  Essentially, the FDA required Orexigen and Takeda to conduct the cardiovascular safety trial of Contrave prior to marketing approval, not post-marketing as recommended by the Advisory Committee. The safety trial required by the FDA will be neither fast nor inexpensive.

As a result of the FDA ruling, what we called “the pall of gloom” descended once again on the antiobesity drug field. Forbes’ Matthew Herper, for example, declared the antiobesity drug field “effectively dead”. Herper further said, “The clear lesson is that weight-loss medicines simply do not have enough of a benefit to justify any risk – and that this makes getting them approved just about impossible.”

If you click on the “metabolic diseases” category on the right-hand panel of this blog, you will see that we have quite a number of blog articles on obesity, usually in the more holistic context of metabolic diseases–obesity, type 2 diabetes, and metabolic syndrome (which is a major risk factor for cardiovascular disease). In these articles, you will see that we are not negative about antiobesity drug development. However, we are–and have been for some time–quite negative about developing appetite suppressant drugs that address common neurotransmitter receptors in the CNS.  Such agents might be expected to have significant adverse effects, since their targets are involved in multiple CNS and/or peripheral tissue pathways. They also tend to have low efficacy.

If you read our articles, you will see that there are several companies that have strategies to develop antiobesity agents that are not appetite suppressants, and that are being–or can be–developed for diabetes and/or metabolic syndrome in addition to obesity.  A common strategy is to develop diabetes/obesity drugs first for diabetes, resulting in easier FDA approval. Such drugs may later also be developed for obesity, after they prove to be safe and to induce weight loss in diabetes trials. For example, Novo Nordisk is following this strategy with the development of liraglutide (Victoza), which is already approved for treatment of type 2 diabetes.

Other established companies are pursuing different strategies, such as Amylin/Takeda’s development of pramlintide/metreleptin for obesity. This is really a metabolic syndrome-based approach to obesity. Indeed, Amylin (whose assets have passed on to AstraZeneca as of early 2014) had been developing metreleptin as a single agent for treatment of diabetes and high triglycerides in patients with lipodystrophy.

Then there are several young companies covered in this blog that are developing antiobesity treatments via innovative biology-driven strategies. Two of these companies, Energesis and Acceleron, are developing antiobesity therapies that target brown fat. Such an approach is really a metabolic syndrome-based one, and might also be applied to various diabetes and/or cardiovascular indications for easier regulatory approval.

Meanwhile, a News and Analysis article in the January 2011 issue of Nature Reviews Drug Discovery lists several agents not covered in our blog. One agent, tesamorelin (Theratechnologies/Merck KGaA’s Egrifta) was approved by the FDA in November 2010 as the first and only treatment indicated to reduce excess abdominal fat in HIV-infected patients with lipodystrophy. Tesamorelin is a synthetic analogue of growth hormone–releasing factor — a hypothalamic peptide that acts on the pituitary to stimulate production and release of human growth hormone. This drug is now in a Phase 2 clinical study for treatment of human growth hormone deficiency associated with abdominal obesity. This represents a potential personalized medicine approach for treatment of a specific population of obese patients. Such an approach may be looked at more favorably by regulatory agencies than a “diet pill” for the general obese population.

As we also discussed in another article, John C. Lechleiter, Ph.D., the chairman, president and CEO of Lilly, outlined the need for “public policies that enable and reward medical innovation”, especially in the metabolic syndrome/diabetes/obesity therapeutic area. This includes “creation of a systematic and transparent regulatory approach to assessing the benefits and risks of new medicines.” Dr. Lechleiter noted the ongoing discussions with the FDA on the PDUFA, which is up for reauthorization in 2012. He sees these discussions as offering an opportunity for negotiation between industry and the FDA to achieve these ends.

We hope that industry and the FDA can work toward a more favorable environment for the approval of safe and efficacious antiobesity drugs. And Dr. John Jenkins, director of the FDA office of new drugs, said that the FDA was “committed to working toward approval” of new obesity drugs, “so long as they are safe and effective for the population for which they are intended.” Nevertheless, we do not see the FDA approving a minimally-efficacious CNS-acting appetite suppressor for the general obese population any time in the foreseeable future.

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