What do we know about the two drugs against Covid-19 from Astrazeneca and Merck

On the one hand a mix of monoclonal antibodies, on the other a pill to be taken by mouth: according to the studies available, the two treatments are 50% effective in preventing severe forms of the disease, but how can they really be used?

(Photo by Tiziana FABI / AFP) (Photo by TIZIANA FABI / AFP via Getty Images) Earlier this week news of the US pharmaceutical company Merck's request to the Food and drug administration ( Fda), the drug regulator in the United States, to approve the use of its anti-Covid-19 pill molnupiravir with emergency authorization. And a few hours later, the Anglo-Swedish AstraZeneca also published an update on its monoclonal antibody-based drug AZD7442, announcing (even before there is a scientific publication to confirm it) the results in phase 3 of the trial, in addition to 'having forwarded a similar request for emergency authorization to the FDA.

Two news which, although concerning very different pharmacological solutions, mark a further step towards the arrival on the market of new therapies against coronavirus Sars-Cov-2. And which would seem to have a quantitative factor in common: in both cases, in fact, the medicines have been shown to have in the first instance an effectiveness close to 50% in preventing the serious forms (including mortality) of Covid-19, provided that they are administered sufficiently early. But let's go in order.

The latest on AstraZeneca monoclonal antibodies

The drug AZD7442 is certainly not a new entry in the panorama of potential therapies against Covid-19. Wired and many newspapers were talking about it a year ago, in October 2020, and in February of this year the phase 3 clinical trial called Tackle had already started. Study that, at least according to the company's public announcements, would now be successfully concluded, making an imminent green light from the various regulatory agencies, starting with the US one, plausible.

From a more technical point of view- scientific, AZD7442 is a solution to be administered by intramuscular injection consisting of a combination of two different monoclonal antibodies: tixagevimab (AZD8895) and cilgavimab (AZD1061). These, also called long-acting antibodies (Laab, long-acting antibodies), act directly on the spike protein of the coronavirus Sars-Cov-2 by inhibiting its ability to replicate within the human body, and are obtained by a process of B lymphocyte engineering of patients recovered from Covid-19.

According to the data obtained from a group of about 900 frail patients involved in the trial, AZD7442 (administered in addition to the other standard therapies) is capable of halving the mortality of infected patients and also halves the frequency of severe and very serious cases. All this if administered early in the initial stages of the disease, and in any case no later than 7 days after the onset of the first symptoms.

Naturally, AstraZeneca is not the only existing formulation based on monoclonal antibodies. For example, there are also those developed by Regeneron and Eli Lilly, based on different monoclonal antibodies. The difference, at least as stated by the company itself, is that AZD7442 seems to be promising not only to treat patients who are already positive, but also as a pre-exposure prophylaxis to the virus, since once injected the antibodies would remain in circulation for at least 9 months. . On the efficacy for antiviral prophylaxis, however, there are no supporting studies and the possible marketing authorization that should arrive would concern only the use for the initial stages of the disease.

The anti pill Covid-19 by Merck

Very different in administration, since it is a tablet to be taken by mouth, is the solution proposed by Merck (better known in Italy as Msd) and Ridgeback Biotherapeutics, always to intervene in the early stages of the disease. Based on a phase 3 clinical study conducted on nearly 800 fragile patients, the pill based on the antiviral molnupiravir would be able to halve the probability of death and lead to severe or very serious forms of Covid-19. Always assuming that the remedy is taken when the disease still has "moderate to mild" forms. A result that has led to an acceleration of the path to obtain authorization, and which could mark an important step forward in reducing the impact of the pandemic on national health systems.

Confident in the success of the emergency approval process , Merck also announced that it has already started mass production of the drug (assuming the economic risk), aiming to have enough pills to cover the entire treatment cycle for 10 million by the end of this year. of patients. The treatment cycle requires the small capsules (brown in color) to be taken twice a day for 5 days, for a total of 10 total administrations. Production between now and December amounts to 100 million capsules, and 17 million would have already been purchased by the US government, which paid $ 1.2 billion.

The reason for the high expectations for molnupiravir it is not just the ease of administration. Once authorized, it would be the first drug that acts directly against the Sars-Cov-2 virus, unlike others in current use (such as remdesivir) which are less specific and not very effective. It would also pave the way for the use of combination therapies with other drugs, allowing an even higher overall efficacy on the patient.

Anti Covid-19 drugs and vaccines

Naturally the pill developed by Merck is not a direct competitor of vaccines, as it would be administered in the early stages of the disease and not as a drug for prophylaxis. Slightly different, however, is the discourse for the formulations based on monoclonal antibodies, which - if they were also authorized for use as a preventive therapy - could be a valid alternative to vaccines for immunosuppressed patients, that is, who are not able to develop sufficient antibodies after vaccine administration. There is no doubt, however, that vaccines will remain the primary strategy to combat the pandemic, for at least a couple of reasons. In addition to the excellent effectiveness that the Pfizer and Moderna vaccines currently in use in our country guarantee in preventing severe forms of the disease, there are also important economic reasons. Monoclonal antibody-based therapies have a cost of orders of magnitude higher than vaccines, so it would not be feasible at the time of using them as a mass drug, even if they were authorized for prophylaxis. While for post-infection use (beyond economic issues) they will probably represent an additional opportunity to reduce the number of hospitalizations and deaths related to Covid-19, but it goes without saying that the best solution can only be to prevent infection from the beginning.


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