Hypericin and AIDS

Many people infected with the human immunodeficiency virus (HIV) have incorporated St. John’s wort (Hypericum perforatum L., Clusiaceae) into their self-care regimens, based on laboratory evidence that hypericin and pseudohypericin are active against retroviruses such as HIV (Meruelo et al., 1988; Lavie et al., 1990). According to reports about earlier clinical research, St. John’s wort helped to improve outlook, reduce fatigue, and enhance well-being for people with HIV, but it was unclear whether the improvements were related to antidepressant effects or to direct antiviral activity (Bergner, 1990).

To investigate the safety and antiretroviral activity of hypericin in a clinical setting, a group of American researchers conducted a phase I study of 30 HIV-infected people with CD4 counts lower than 350 cells/mm³ (Gulick et al., 1999). Phase I studies are primarily concerned with assessing the safety of a substance and evaluating side effects that occur as dosage is increased.

This small study, which employed oral and injectable treatment with synthetic hypericin, yielded disappointing results. Not only did the pharmaceutical hypericin demonstrate no antiretroviral activity, it caused severe phototoxicity in 48 percent of the participants. Sixteen of the 30 subjects (53 percent) dropped out of the study early because of side effects. Almost all of the participants taking either oral or injectable hypericin experienced some degree of phototoxicity, which caused a painful red rash in areas exposed to light.

The investigators speculated that the lack of anti-retroviral activity could be attributed to the fact that the high incidence of side effects made it impossible for them to achieve sustained blood levels of hypericin sufficient to inactivate the virus. It is important to note that since this study utilized a synthetic hypericin preparation, its results cannot necessarily be extrapolated to St. John’s wort standardized extract or whole plant preparations.

For the study, the participants were divided into four groups. Three of the groups were treated with intravenous hypericin (0.25 or 0.5 mg/kg twice weekly or 0.25 mg/kg three times weekly) and one received oral hypericin (0.5 mg/kg daily). The antiretroviral activity of the synthetic hypericin was assessed by measuring changes in CD4 cell counts, HIV p24 antigen level, virus titer, and HIV RNA copies. There were no detectable changes in any of these parameters. Adverse effects were evaluated weekly and graded according to a four-point scale, with grade 1 representing the mildest adverse reaction and grade 4 representing the most severe reaction. Grade 3 phototoxicity, which was observed in 48 percent of the study subjects, was defined as "intolerable erythema or numbness (or both), temperature sensitivity, and pain despite long-term analgesic therapy." No grade 4 phototoxicity was reported.

The investigators suggested that even though the synthetic hypericin proved too toxic to allow assessment of its clinical value in this study, other applications might hold more promise. "The potent antiviral activity of hypericin in vitro has led to its use in the ex vivo treatment of blood components," they noted. "This approach avoids phototoxicity and uses the well-described enhancement of the antiviral effect of hypericin by light." – Evelyn Leigh