In short
Plasmodium falciparum, strain NF54, sporozoites — known as PfSPZ Challenge (NF54) — is an investigational substance used to deliberately expose healthy volunteers to malaria in controlled clinical trials. It is a solution for injection given intravenously and has no marketing authorisation. In one completed Phase 2 trial, 32 participants received this challenge to test whether a weekly dose of atovaquone-proguanil could protect against malaria.
Key points
- PfSPZ Challenge (NF54) is an investigational malaria challenge agent given by intravenous injection.
- It is used in controlled human malaria infection studies to test preventive medicines.
- The registered trial was a Phase 2 study that has been completed.
- The trial enrolled 32 healthy volunteers without prior malaria immunity.
- The main goal was to measure the proportion of protected volunteers after weekly atovaquone-proguanil.
- Protection was defined as no amplifying parasitaemia for 21 days after challenge.
What is PfSPZ challenge (NF54)?
Plasmodium falciparum, strain NF54, sporozoites is an investigational substance with no marketing authorisation in the product records. Its product name in the registry is PfSPZ Challenge (NF54), supplied by University Hospital Tuebingen. The substance is classified under parasitic diseases in the registry and is used as a test agent in one trial. Sporozoites are the parasite stage transmitted by mosquito bites; they first infect the liver before releasing forms that invade red blood cells and cause malaria disease.
How does PfSPZ challenge (NF54) work?
Sporozoites are formed inside oocysts in the mosquito midgut and become fully infectious after colonising the insect salivary glands, where they remain quiescent until transmission. When injected intravenously into a volunteer, the sporozoites travel to the liver, transform into replicative forms, and subsequently release thousands of merozoites that invade red blood cells and initiate malaria. In challenge studies, this deliberate exposure lets researchers test whether a preventive medicine stops the parasite from establishing a blood-stage infection.
Which conditions is it used or studied for?
- Malaria — in the registered trial, PfSPZ Challenge (NF54) was used to induce a controlled malaria infection in healthy volunteers so that the protective effect of a weekly antimalarial medicine could be measured.
How is PfSPZ challenge (NF54) given?
PfSPZ Challenge (NF54) is a solution for injection given by intravenous injection. In the registered trial, the challenge dose was 3200 sporozoites administered intravenously. The registry also notes that in one product record the substance is part of a fixed combination.
What do the clinical trials show?
One completed Phase 2 trial investigated PfSPZ Challenge (NF54) in malaria. The study enrolled 32 healthy, non-immune volunteers and tested whether a weekly oral dose of atovaquone-proguanil (250/100 mg) could protect against malaria after intravenous challenge with PfSPZ Challenge (NF54). The primary efficacy endpoint was the proportion of protected volunteers, defined as the absence of amplifying parasitaemia — a rising number of parasites in the blood — for 21 days after challenge. The study also measured a primary safety endpoint relating to the number of adverse events.