To my knowledge, for the herpesvirus subset of ME/CFS, it is only Dr Martin Lerner and Prof Montoya + Dr Kogelnik who have conducted published trials on the efficacy of Valtrex and Valcyte for treating ME/CFS.
Only one of Montoya and Kogelnik's
studies was double-blind and placebo-controlled. His results in this study were not overly impressive, but did show that patients on Valcyte for a course of 6 months were 7.4 times more likely to be classified as responders than the placebo patients.
However, the issue with Montoya's studies is that ME/CFS patients taking Valtrex and Valcyte generally do not begin showing improvements until around 3 or 4 months, and the full benefits only manifest after around 2 years or so — we know this from Lerner's studies.
All of Montoya's three studies were for 6 months duration only, and this is not really enough time for the full benefits of treatment to manifest.
Lerner's study on 142 ME/CFS patients was better in that it was conducted for a total of 6 years of Valtrex or Valcyte treatment, but it was not placebo controlled. This study is interesting, because it shows the slow improvement that patients make over the years, with most improvement occurring with the first two years.
If you look at the second table in
this post, you see that slow improvement (as measured by the Energy Index Point Score) that occurs on these antivirals.
That's a question I have always wondered about: is it only ME/CFS patients with high titers to EBV, HHV-6 and/or cytomegalovirus who respond to Valtrex/Valcyte, or do patients with low herpesvirus titers also respond?
Montoya investigated this question in
this study, and found that:
So the initial baseline titers did not seem to have much bearing on who responded and who did not. Although he found that:
So the patients with higher titers initially seemed to respond a little better.
Thus the results of this paper seem to suggest that you can also benefit from Valcyte (valganciclovir) even if you have low herpesvirus titers.
What can we conclude from that? As far as I can see, it could mean: (1) some ME/CFS patients may have low level herpesvirus infections causing their ME/CFS symptoms, but these infections do not always create high titers; (2) Valcyte is able to improve ME/CFS by a mechanism unrelated to its antiviral action on herpesviruses.
To my knowledge, however, ME/CFS specialists are still testing for high herpesvirus titers or high enterovirus titers, and treating patients with antivirals on that basis (Valtrex, Famvir or Valcyte, etc for herpesviruses; and oxymatrine, etc for enteroviruses).