Pfizer's oral antiviral drug Paxlovid holds out promise in the fight against Covid. And with 19 Indian drug-makers now allowed to make a similar version of the anti-viral, their local regulatory journey will soon start.

The drug, Nirmatrelvir (given along with a low dose of Ritonavir), is the second oral antiviral that is seeing extensive collaboration with local generic companies after Merck’s Molnupiravir. On Thursday, the Medicines Patent Pool (MPP) announced signing of sub-license agreements with 35 companies globally, to make generic versions of Pfizer’s oral Covid treatment.

On the road ahead for the companies in terms of local clinical trials and prospects against Molnupiravir and other existing treatments, a representative with a sub-licensee drugmaker, said: "The acceptability of the drug depends on the virulence of the virus. In case of a mild infection, people may not opt for aggressive treatment and hence, there may not be great off-take of the drug whether it is Molnupiravir or Nirmatrelvir. At present, there is not much clarity about the quantifiable opportunity," a source at one of the pharma players, which has signed the sub-license agreement."

In Molnupiravir’s case, the Drug Controller General of India (DCGI) had granted emergency use nod last December to Merck Sharpe Dohme (MSD, or Merck in the US and Canada) and Ridgeback’s Molnupiravir. A collaboration of five pharma players had then undertaken clinical trials to get regulatory approvals.

On a sticky wicket

The drug has been on a sticky wicket though, since the Indian Council of Medical Research (ICMR) had opined that the current clinical window of application of Molnupiravir appeared "extremely narrow with relevance only to a few". And based on the currently available synthesised evidence, the National Task Force members unanimously agreed not to include Molnupiravir in the national treatment guidelines.

Molnupiravir's effectiveness of reducing risk of hospitalisation or death was 30 per cent while being effective in the unvaccinated elderly.

Earlier this month, in its update on treatment guidelines to include Molnupiravir, WHO stated that since it is the first oral antiviral being used for Covid, "there is little safety data". It also noted that "because of these concerns and data gaps, Molnupiravir should be provided only to non-severe Covid patients with the highest risk of hospitalization".

On the other hand, Pfizer's Paxlovid holds promise for coverage of a large number of population across low- and middle-income countries, including India. The effectiveness of reducing risk of hospitalisation or death is found to be 89 per cent (as per Phase 2/3 trial data) and also on those with vaccinated or prior infection. According to Pfizer, Nirmatrelvir has shown consistent in vitro antiviral activity against earlier and current variants of concern (Alpha, Beta, Delta, Gamma, Lambda, Mu and Omicron).

However, the approval for the commercial roll out will be based on the drug trials on Indian population.

According to the MPP agreements, 35 generic drug makers from across 12 countries have been granted the sub-licences to make the generic version of the drug. India has the most number of companies - 19 drug makers under the sub-license that includes three players Divi's Lab, Arene Lifesciences and SMS Pharma for exclusively manufacturing the drug substance, while 15 others including the noted players such as Cipla, Torrent Pharma, Sun Pharmaceuticals, Emcure, Granules, Glenmark, Hetero, Cadila Pharma among others to make drug substance and product both. One company, Strides has been granted the sublicense to make only the product.

After India, China has the second most number of sublicensed companies, at five, followed by South Korea at two.

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