Role of HPBCD in development of Pfizer’s novel COVID-19 oral antiviral treatment candidate

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Pfizer’s breakthrough drug candidate PF-07321332 used in combination with ritonavir was poven to successfully reduce the risk of hospitalization and death related to COVID-19 infection [1]. Submission of clinical study data as part of Pfizer’s ongoing rolling submission to the U.S. FDA for Emergency Use Authorization (EUA) is expected in the very near future [2].

According to a prior publication of Pfizer’s key researchers, HPBCD is a potent solubilizer of PF-07321332 [3]. Upon the determination of preclinical pharmacokinetics parameters of the drug candidate, the plasma concentration–time data were conducted in male gender of each species (Wistar-Han rats and cynomolgus monkey). Intravenous (iv) doses for PF-07321332 were administered as a solution in 10% DMSO/30% PEG400/60% deionized water to rats, but 5% (v/v) PEG400:95% (v/v) of 23% 2-hydroxypropyl-β-cyclodextrin in aqueous sodium phosphate buffer pH = 6.0 was administered to the monkeys.

It is not yet public whether HPBCD is applied in the final oral dosage product (that will be marketed under the brand name PAXLOVID™), the role of the cyclodextrin solublilized model iv. solution was nevertheless crucial in the preclinical drug development phase. At least the monkeys were not exposed to DMSO, unlike those unlucky rats…




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  1. Nature has published that his new formulation of Pfizer (Paxlovid) together with MerckÍs molnupiravir could be a game-changer for the pandemic. The companies say that both drugs significantly cut the risk of hospitalization and death in vulnerable people, if used early. Scientists are poised to discover how well the drugs will work in the real world, their safety for a wide range of people, their effectiveness against viral variants, and how easily they will get to the people who need them most. There’s also the concern that the coronavirus could become resistant to antivirals.
    Ledford, H. COVID antiviral pills: what scientists still want to know. 2021

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