Margaret A. Hamburg, M.D., will step down as FDA commissioner at the end of March, the agency confirmed this morning.

The resignation will end a nearly six-year tenure during which Dr. Hamburg led the agency in implementing policies designed to speed up new-drug reviews, and extending FDA’s regulatory reach to new products and technologies such as biosimilars, lab-developed tests, and direct-to-consumer (DTC) genetic tests.

FDA named its chief scientist, Stephen Ostroff, M.D., as interim commissioner pending approval of a new permanent head of the agency by Congress.

“The decision was not easy,” Dr. Hamburg said in a statement, adding: “While there is still work ahead (and there will always be), I know that I am leaving the agency well-positioned to fulfill its responsibilities to the American public with great success.”

The patient advocacy group Friends of Cancer Research agreed with Dr. Hamburg’s self-assessment.

“She has changed the direction of the FDA, creating an environment of science-based collaboration that has fostered a new era of regulatory science focused on expediting the best treatments to patients,” Ellen Sigal, chair & founder of Friends of Cancer Research, said in a statement. “Commissioner Hamburg's leadership and her commitment to patients are unsurpassed.”

Dr. Hamburg also sought to position the agency as one that balanced the interests of public health for safety and effectiveness, and of the biopharma industry for rules that encouraged drug commercialization. Industry representatives complained often and loudly in the early years of her tenure that the balance had swung too far toward red tape and risk-aversion in new-drug reviews due to the Food and Drug Administration Amendments Act of 2007, which tightened new-drug reviews with the goal of preventing approval of blockbuster drugs with deadly side effects like Vioxx and Celebrex.

Those complaints began to subside after 2012, when President Obama signed into law the Food and Drug Administration Safety and Innovation Act (FDASIA). Among provisions of the law was the “Breakthrough Therapy” designation calling for earlier and more frequent communication, plus closer guidance, by the agency with drug developers, with the goal of speeding up reviews and decisions. Dr. Hamburg’s office implemented breakthrough therapy designation and other expansions to FDA’s expedited-approval pathways.

“These programs have proven invaluable in bringing groundbreaking new therapies to patients more efficiently, while maintaining the FDA’s high standards for safety and efficacy. In 2014, the FDA approved more than 40 new drugs, the most in nearly two decades,” Biotechnology Industry Organization (BIO) President and CEO Jim Greenwood said in a statement thanking Dr. Hamburg for her FDA service. “We look forward to continuing to work with Dr. Hamburg and her successor to ensure that the FDA’s regulatory capabilities and science continue to keep pace with the tremendous progress taking place in biotechnology innovation.”

Also praising Dr. Hamburg today was John Castellani, president and CEO of Pharmaceutical Research and Manufacturers of America (PhRMA): “PhRMA salutes the work of Commissioner Hamburg and recognizes her significant contributions to the thoughtful regulation of medicines, including science as a basis for better regulatory decisions. For nearly six years, and to the direct benefit of patients, Commissioner Hamburg has demonstrated strong leadership and an unwavering commitment to collaboration with all stakeholders.

Industry executives surveyed for a report issued last month by PricewaterhouseCoopers also agreed that FDA had been more responsive to drug developers. One finding showed 70% of executives surveyed believed that FDA offered “more applicable guidance, rules and regulations” in the past two years, during which 78% believed FDA “has improved the quality and frequency of its communications.”

The report also showed 71% of executives surveyed “believe that the FDA can accelerate approval programs by balancing swifter approval with increased post-market surveillance.”

Under Hamburg, FDA began efforts to regulate biosimilars in 2012 but continued to lag behind Europe, where regulators have authorized 19 biosimilars. On January 7, FDA’s Oncologic Drugs Advisory Committee recommending agency approval of the first such product in January—a version of filgrastim developed by Novartis’ Sandoz unit.

The agency also showed increasing willingness to regulate newer technologies. Last year, for example, the FDA issued draft guidance to regulate laboratory-developed tests (LDTs) that it deems “high-risk” as Class III medical devices, drawing opposition from academic labs and support from diagnostics manufacturers.

In November 2013, FDA confronted 23andMe by ordering it to stop selling its Saliva Collection Kit and Personal Genome Service (PGS), accusing the genetic test developer of violating the Federal Food, Drug and Cosmetic Act of marketing the test without first obtaining clearance or approval from the agency. While advocates of DTC testing denounced the FDA action as a regulatory overreach, the company established a dialogue with the agency and moved to pursue approval for its kit. On January 12, 23andMe CEO Anne Wojcicki said the company entered 2015 with “many employees working diligently on our FDA submission.

Speculation on a potential successor to Dr. Hamburg has focused in part on Robert Califf, M.D., a cardiologist and vice chancellor of clinical and translational research at Duke University, since last week he was appointed by Dr. Hamburg as deputy commissioner for medical products and tobacco.

Dr. Califf’s new FDA position entails in part overseeing clinical, scientific and regulatory initiatives in areas that include personalized medicine, orphan drugs, pediatric science, and the advisory committee system. Within his purview are several centers within FDA, including the Center for Drug Evaluation and Research, the Center for Biologics Evaluation and Research, the Center for Devices and Radiological Health, and the Center for Tobacco Products.

Dr. Hamburg, 59, became the FDA’s 21st commissioner on May 18, 2009, following appointment by President Barack Obama. Before taking the agency’s helm, she was senior scientist at the Nuclear Threat Initiative, a foundation committed to reducing the public safety threat posed by nuclear, chemical, and biological weapons. FDA is an agency within the U.S. Department of Health and Human Services, where she was assistant secretary for policy and evaluation after serving as commissioner of the New York City Department of Health and Mental Hygiene from 1991-97.

Dr. Hamburg communicated her resignation through a memorandum to FDA staff. In it, she said she was stepping down “”with very mixed emotions,” and that her tenure as commissioner “has been the most rewarding of my career.”

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