How the two Cuban COVID-19 vaccines that have reached phase III but have yet to receive regulatory approvals work

Cuban scientists are working in four COVID-19 vaccine candidates: Sovereign 1 (in phase II), Sovereign 2 (in phase III) and Mambisa (in phase I) and Abdala (in phase III). A fifth candidate, Sovereign +, is a reformulation of Sovereign 1, intended for those recovering from the disease.

If all phases of testing and approval of the Cuban National Regulatory Agency, one of these vaccines would become in the coming months the first against disease designed and produced in Latin America.

Despite the objections of international science, the president Alberto Fernandez confirmed that he is negotiating the purchase of Cuban vaccines. The Argentine president announced that he had already started negotiations with his Cuban counterpart, Miguel Diaz Canel, To access Sovereign 2 and Abdala, scientific developments against the coronavirus which Venezuelan National Academy of Medicine rated as “Investigational products whose composition, safety or efficacy are not known.” “These are not real vaccines,” the entity warned.

“I was talking with the President of Cuba, with the engineer Diaz Canel. Cuba has done a job that all scientists think is wonderful, very important, in developing a vaccine called Sovereign, which has two versions, which is in phase III. I asked him what his production capacity was, he told me about the difficulties he had to work and I offered to work together so that all of Latin America could have access to a vaccine.», He assured Fernandez on Radio 10.

The Venezuelan National Academy of Medicine alerted in recent days on lack of reliable information on the possible inoculant after the dictator Nicolas maduro will announce that 2 million doses of Abdala, one of the Cuban candidates against the disease, will be produced per month in Venezuela.

But, how do they work? All Cuban prototypes are based on inoculate a coronavirus spike protein, the part that binds to infected cells, to produce an immune response. Sovereign 2, in which there are more expectations, it also adds an immune response enhancer. The latter It is injectable, two application doses are planned, with two week intervals between each, in addition to a possible reinforcement. And this brings something new in this area: does not need freezers for its maintenance, a further attraction for the poor countries of the world.

It is a conjugate vaccine because it has an antigen that fuses with a carrier molecule to improve its stability and effectiveness. In its development, a tetanus toxin to the protein that the virus attaches to the cell. In this way, when the virus tries to enter it using this protein, an immune reaction is generated against the toxin that the protein carries, with which It’s blocked his entry into the cell. Experts claim that Sovereign 2’s technology has already been used successfully in other vaccines manufactured in Cuba.

March 21th, the island country has announced that it will start a new test the efficacy of the vaccine developed by the Finlay Vaccine Institute (IFV) at an intervention study with 150,000 volunteers of Havana, as part of phase III of its development. The trial, approved by the State Center for the Control of Drugs and Medical Devices, assesses the direct and indirect effects of vaccination on “population cohorts” risk of infection, disease and spread of the epidemic.

While the Sovereign uses an antigen obtained from mammalian cells in various formulations; Abdala uses an antigen taken from yeast, also in various formulations. The vaccine, produced by the Center for Genetic Engineering and Biotechnology (CIGB), inserts genetic information into a less evolved single-celled microorganism (Yeast Pichia Pastoris) and is based on the long experience and impressive track record of ICOLD, whose hepatitis B vaccines have been used in Cuba for 25 years.

The past April 3, the application of the first dose was completed of this vaccine in 48,000 volunteers from the eastern provinces of Santiago de Cuba, Guantánamo and Granma, and on April 5, the second injection of this vaccine began to be administered, of which three doses (0, 14 and 28 days) will be administered in two groups, one experimental and one control. On the same day, the application of the second dose of Soberana 2 to the volunteers included in the phase III trial in Havana began.

“It is a moment of great pride for the country”, said at a press conference the deputy director general of the IGBC, Marta Ayala. The scientist highlighted the good safety and immunogenicity results obtained during the first two stages of testing this formula, carried out in Santiago de Cuba between December and February last and in which nearly 800 people participated (132 in phase 1 and 660 in phase 1). of them).

Laboratories of BioCubaFarma, entity to which 32 institutes, research centers and biotechnology and pharmaceutical production industries belong, more than 300,000 doses of Soberana 2 and Abdala have already been released, and Its officials ensure that they have the capacity to produce 100 million bottles before the end of 2021. The stated objective is have at least one vaccine ready in summer and start mass vaccination in July and August. It is expected that half of the population will be vaccinated in September and all Cubans before the end of the year.

“The results to date are encouraging: both vaccine candidates have been shown to be safe and able to generate specific antibodies against the virus. We are optimistic ”, declared shortly before the start of phase III Eulogio Pimentel, vice-president of the group of companies BioCubaFarma, which produces eight of the 13 vaccines that are part of the island’s national immunization program.

Despite their limited material resources, Cuba is responsible for the development of two of the 23 coronavirus vaccines that have entered Phase III trials around the world. For the country, succeeding in crowning the development of its vaccines is of crucial importance because of the scientific and political prestige it represents, but also for economic reasons at a time when the island is going through one of the worst crises in its history.

The bet of the Caribbean country all to their own vaccine which they intend to export, because has not acquired doses on the international market nor joined the Covax mechanism, created under the auspices of the World Health Organization (WHO) to promote equitable access to immunization for low- and middle-income countries.

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