FDA veteran questions science behind antibiotics fast track
The Food & Drug Administration (FDA) has awarded fast-track qualified infectious disease product (QIDP) status to iclaprim, made by Motif Bio, for acute bacterial skin and skin structure infections.
The QIDP designation is provided under the Generating Antibiotic Incentives Now Act (GAIN Act) and makes iclaprim eligible for certain incentives, including priority review and fast track designation.
The broad-spectrum antibiotic is designed to be effective against multidrug-resistant bacteria and does not yet have marketing approval in the US.
'This drug should not be developed further'
The FDA began offering QIDP designations to antimicrobials designed to treat serious and life-threatening infections after the GAIN Act was passed in the US Congress in July 2012. The aim was to entice pharma companies back into developing antibiotics.
Back in 2008, following a phase III trial, a request to the FDA for approval to market iclaprim was declined. Three other antibiotics failed to gain approval for commercialization around the same time. Two of these – dalbavancin and oritavancin – were subsequently approved by the FDA last summer.
Motif said it has reviewed all preclinical and clinical data and believes “iclaprim can be rapidly returned to late stage clinical testing with some improvements to the original development program.” The company added the regulatory environment for antibiotics has become more favourable to the approval of potential antibiotic compounds.
Not everyone views this as a positive development. “This drug has been studied in humans before for skin infections and failed to show it was beneficial to patients,” said John Powers, clinical professor of medicine at George Washington University and former Lead Medical Officer for Antimicrobial Development at FDA. “At the advisory meeting [of the FDA] the advisors commented this drug should not be developed further given the results of the studies presented.”
Moreover, “this drug is mostly for Gram-positive organisms for which there are over dozen treatment options even for resistant organisms like MRSA, but the real need is for antibiotics against life threatening disease due to Gram-negative [bacteria].” Powers sees QIDP and GAIN as hugely problematic because they do not encourage development of better antibiotics.
“Virtually everything qualifies. All that is required is show activity in a test tube against a rather comprehensive list of pathogens that include most organisms that cause human disease and for which many treatment options are already available. It doesn’t say the new drug has to be better than existing therapies,” he said.
The FDA expert expressed concern in July’s Annals of Internal Medicine that the drug industry is forgetting past lessons about what constitutes good evidence. In the 1960s, the FDA removed antibiotics from the market due to a lack of efficacy; pharma companies had been relying on what they called a "totality of evidence" – a mishmash of preclinical and poorly controlled human studies.
Now the focus has returned to “what happens in bacteria, but it is what happens in people that’s important,” argued Powers.
Broad-spectrum
Iclaprim is the lead candidate of UK-based Motif Bio, a clinical-stage biopharma. The company says the antibiotic exhibits potent activity against Gram-positive clinical isolates of many genera of staphylococci, including MSSA and MRSA.
It is a dihydrofolate reductase inhibitor originated discovered by F. Hoffman-La Roche Ltd, later licensed to and developed by Arpida, which sought market approval in 2008.
If Motif Bio gains approval, the drug will be eligible for an additional five-year extension of Hatch-Waxman exclusivity, for a total of ten years of market exclusivity.
The FDA has granted 78 QIDP designations for 53 unique chemical entities to date. Five QIDP antibacterial entities and one QIDP antifungal new molecular entity met the criteria for a 5-year GAIN exclusivity extension, an agency spokesperson noted.
