The patch - developed by Corium International - delivers donepezil, the active ingredient in Pfizer's $3.5bn Aricept brand and various generic copies. In May, the FDA agreed that Corium could secure approval for the patch based on bioequivalence to Aricept rather than efficacy studies.
That decision has saved Corium "at least $30m" in development costs and sets it on course to file for the seven-day Corplex patch in mid-2018, according to the company's chief executive Peter Staple, who maintains that the market opportunity for a donepezil patch is "compelling".
There is currently one patch product on the market for AD - Novartis' Exelon (rivastigmine) - which achieved sales of around $900m last year and has retained market share despite the availability of generics of oral rivastigmine.
Both rivastigmine and donepezil act by cholinesterase inhibition, boosting neurotransmitter levels in the brain in a bid to slow down declines in memory and cognition. These drugs remain the most commonly-used treatment approach for AD - despite having relatively limited efficacy - as efforts to develop other treatments have so far proved unsuccessful.
Exelon has cemented its position in the AD market because it can be a useful option for patients who cannot take medicines by mouth for whatever reason, and also because the transdermal delivery route reduces side effects.
Staple believes its donepezil patch could do better however. Not only is donepezil much more widely prescribed than rivastigmine (45 percent and 9 percent market share respectively), but the Corplex patch can be given once-weekly, while Exelon needs to be changed every day.
"We have an opportunity to address a clear unmet need for physicians, patients and caregivers in a large and growing market," he said.
Moreover, the FDA's decision on Corplex donepezil could also suggest a shorter 505(b)2 regulatory pathway for Corium's Corplex formulation of another AD drug - the glutamate NMDA antagonist memantine which is the active ingredient in Merz/Allergan's Ebixa/Namenda brands and accounts for around 40 per cent of the AD market.
The company is hoping for positive feedback on a bioequivalence route for this once-weekly patch as well, and could get a verdict in the third quarter. Having both patches would give Corium a patch treatment option both for first-line AD patients and those who have progressed into ore advanced stages of the disease.
Analysts at Edison say Corium could get approvals for four patch products in the 2019-2021 timeframe, including a transdermal formulation of teriparatide - the active ingredient in Eli Lilly's $1.4bn osteoporosis product Forteo.
The teriparatide product uses a microneedle technology platform developed by Corium - called MicroCor - that is specifically designed for biological drugs.