Monoclonal antibody to prevent malaria infection

In October 2021, the WHO recommended the use of the Mosquirix vaccine as a preventive measure against infection, however, it offers partial protection with an estimated efficacy of 36.3% after 4 years of follow-up. Although there has been a great development in terms of malaria vaccination, other strategies are needed to reduce the global incidence of the disease and its high mortality, sub-Saharan Africa is the region most affected by the disease and it is estimated that 80% of deaths there be in children under 5 years of age.

Read too: Malaria in pregnancy: what are the particularities?

Therefore, a phase 1 open-label clinical trial was carried out in the United States to evaluate the use of a monoclonal antibody (L9LS) to protect against malaria. Monoclonal antibodies have been shown to be effective in preventing the disease by acting in the pre-erythrocytic phase, neutralizing sporozoites. This approach differs from vaccines in that it is not influenced by some variables, such as previous exposure to malaria, age and immunodeficiency. L9LS is part of the new generation of monoclonal antibodies against malaria, being three times more potent than the previous generation in pre-clinical trials.

Monoclonal antibody to prevent malaria infection

methods

Thus, this phase 1 trial aimed primarily to assess the efficacy and safety of the medication and, secondly, to assess the pharmacokinetic properties and protective effect after two to six weeks of controlled exposure to malaria. A total of 27 healthy adult participants (aged 18-50 years) who did not have the disease or were vaccinated were selected, 18 received the L9LS as follows:

  • 5 patients received 1 mg/kg intravenously;
  • 4 patients received 5 mg/kg intravenously;
  • 5 received 5 mg/kg subcutaneously;
  • 4 received 20 mg/kg intravenously;
  • The other participants were controls.

Participants were exposed to mosquito anopheles stephensi infected by P. falciparum (strain 3D7) and parasitaemia was defined as a positive PCR result. Participants were considered protected if they did not develop parasitemia after 21 days.

Malaria prevention trial results

Regarding the safety of the tested medication, all symptoms associated with the application site were mild to moderate and self-limited, with no significant difference in the mode of administration (intravenous or subcutaneous). There was no report of an infusion reaction and only one patient developed local adenopathy that was drug-related and resolved spontaneously within 29 days.

Regarding pharmacokinetics, the highest serum concentration was obtained with the dose of 20 mg/kg intravenously and the lowest with 1 mg/kg intravenously. Of the 18 participants who received the monoclonal antibody, one was lost to follow-up, and 15 (88%) were protected from infection. There was no infection in any of the patients who received doses of 5 or 20 mg/kg intravenously. Two of the 10 participants who received the 1 mg/kg intravenous or 5 mg/kg subcutaneous doses and all controls developed parasitaemia. Medication efficacy was seen at serum concentrations starting at 9.2 µg/ml and the estimated half-life was 56 days.

Know more: Malaria: early diagnosis and treatment strategies

practical message

Despite being a small, phase 1 study, whose primary objective is to assess safety and side effects, and which, for this very reason, selects healthy people from a non-endemic region, the findings are encouraging. They bring as a future option a strategy with apparently good durability, since the drug had a long half-life. In addition, high potency means that little volume of drug needs to be administered, reducing costs. This is all critical in disease-endemic regions, which are generally poor. Another relevant point is that the possibility of subcutaneous administration is interesting when we think about protecting the pediatric population.

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