Merck & Co is the latest company to offer an all-oral therapy for chronic hepatitis C virus (HCV) infection after getting FDA approval for its Zepatier drug.
Zepatier is a fixed-dose combination which combines Merck's NS5A inhibitor elbasvir (MK-8742) with NS3/4A protease inhibitor grazoprevir (MK-5172) and has been cleared by the US regulator for use with or without ribavirin in patients with HCV genotypes 1 and 4.
The combination launches into a market that has been transformed by the arrival of all-oral therapies that have supplanted older, injectable-based treatment based on interferon alfa. The new regimens have far fewer side effects than interferon and can also provide a functional cure from the infection in a matter of weeks rather than months.
The undisputed market leader at the moment is Gilead Sciences with its Harvoni (sofosbuvir/ledipasvir) combination and single-agent product Sovaldi (sofosbuvir), with AbbVie also pressing for market share with its rival therapy Viekirax/Viekira Pak (ombitasvir/paritaprevir/ritonavir and dasabuvir).
The director of the FDA's Office of Antimicrobial Products - Edward Cox - said the approval of Zepatier "provides another oral treatment option for patients with genotypes 1 and 4 HCV infections without requiring use of interferon".
Patients, doctors and payers have been anticipating the launch of additional oral HCV therapies in the hope that the increased competition will help drive down the cost of treatment.
For example, at undiscounted prices a 12-week course of Sovaldi currently costs $84,000, with Harvoni costing $94,500 and Viekirax set at around $83,000.
Merck has said it will price Zepatier at $54,000 for a 12-week course - well below its rivals - which analysts said could help it become included quickly on payer formularies and potentially reach $2bn in sales by 2020.
Zepatier's approval comes as some states in the US are starting to kick back against HCV drug pricing, with Massachusetts threatening to take legal action against Gilead if it does not cut prices to more affordable levels.
The state maintains Gilead's pricing policy is a threat to public health, echoing concerns raised by presidential candidate Bernie Sanders who has suggested the patents for the drugs should be broken to allow generic drug producers to enter the market.
Sovaldi and Harvoni brought in $3.7bn and $10.5bn in sales respectively in the first nine months of 2015, with AbbVie's drug topping the $1bn mark in the same period. Both companies are also in the process of bringing new combination products to market that are effective against the full range of HCV genotypes (1-6).
In trials, Zepatier given for 12 or 16 weeks was associated with a sustained virologic response (SVR) rate of 94%-97% in patients with genotype 1 HCV - the most common form in the Americas, Europe and some parts of Asia. For genotype 4 - commonly encountered in central Africa - the SVR rate was 97%-100%.