In an article entitled “Clinical Potential of the Acyclic Nucleoside Phoshonates Cidofovir, Adefovir and Tenofovir in Treatment of DNA Virus and Retrovirus Infections” (Clinical Microbiology Reviews, 2003) Erik De Clercq found that both cidofovir and adefovir dipivoxil work well for a wide range of viruses including HHV-6 and were superior to ganciclovir for viruses such as CMV.
Antiviral activity spectrum of the acyclic nucleoside phosphonates
| Virus | Cidofovir | Adefovirdipivoxil |
| Polyomavirus | Yes | |
| Pappillomavirus | Yes | |
| Adenovirus | Yes | |
| HSV-1 | Yes | Yes |
| HSV-2 | Yes | Yes |
| VZV | Yes | Yes |
| CMV | Yes | Yes |
| EBV | Yes | Yes |
| HHV-6 | Yes | Yes |
| HHV-7 | Yes | Yes |
| HHV-8 | Yes | Yes |
| Variola | Yes | |
| Cowpox | Yes | |
| Monkeypox | Yes | |
| Camelpox | Yes | |
| Vaccinia | Yes | |
| MCV | Yes | |
| Orf | Yes | |
| Hepatitis B | Yes | Yes |
| HIV-1 | Yes | |
| HIV-2 | Yes | |
| SIV | Yes | |
| FIV | Yes |
*From De Clercq, Clinical Microbiology Reviews, 2003
Although adefovir (Hepsera), a cousin of cidofovir, showed efficacy in vitro and is available in an oral form for hepatitis B, the dose is considered too small to pass the blood brain barrier in sufficient quantities. Larger doses showed kidney toxicity.
In a study done at the University of Alabama, Long et al found that the selectivity index was higher for cidofovir than either ganciclovir or foscarnet for HHV-6A. The following data was presented in their article entitled “Determination of antiviral efficacy against lymphotropic herpesviruses utilizing flow cytometry” in Antiviral Research (2003):
| EC50 (µg/ml) | In HSB-2 cells | In Sup T1 cells |
| cidofovir | 4.6 mcg/µl | 2.0 mcg/µl |
| foscarnet | 9.5 mcg/µl | 6.3 mcg/µl |
| ganciclovir | 10.6. mcg/µl | 7.6 mcg/µl |
See Experimental & Alternative Treatments
Read about antiviral use in transplant patients with HHV-6 encephalitis
See the Foundation’s interview with Drs. Eric De Clerq and Lieve Naessen’s of the Rega Institute on epilepsy and antiviral treatment
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