Ritonavir + AZT + 3TC
Abstract (Birmingham, England) November 1996
Thirty-one treatment-naive individuals were randomized to begin triple therapy (ritonavir 600 mg + AZT 300 mg + 3TC 150 mg--all 3 drugs were administered twice daily (every 12 hours, bid) simultaneously or to the delayed group where ritonavir was initiated alone followed by the addition of AZT and 3TC three weeks later. The immediate vs delayed comparison is to detect if there is a difference in effect due to the 3-week delay in adding AZT/3TC. Dr. Sven Danner, of the University of Amsterdam, reported the preliminary virological and immunological data from this ongoing open-label two arm study. Dr. Daan Notermans, of the Academic Medical Center in Amsterdam, reported results from a study of the RNA load in the lymphoid tissue from tonsillar biopsies of 6 study participants who continued on treatment in this ritonavir/AZT/3TC study.
Group 1, the immediate group had median baseline RNA, CD4 and CD8 of 5.27 log (about 187,000 copies/ml), 177 cells, and 1,027 cells, respectively. Group 2, which delayed AZT/3TC for 3 weeks, had median baseline RNA, CD4 and CD8 of 5.37 (about 235,000 copies/ml), 134 cells, and 927 cells.
CD4. For group 1 (the immediate group, baseline=177 CD4) at 8 weeks, there was about a 100 cell median increase from baseline (n=16); for group 2 (delayed, baseline= 134 cells), there was about a 75 cell median increase from baseline (n=16); at 12 weeks, the median CD4 increase from baseline was about 130 for group 1 (n=16) and about 80 for group 2 (n=16); at 24 weeks, the median CD4 increase was about 175 for the immediate (group 1, n=9) group and about 100 for the delayed (group 2, n=12) group.
Table 8- Median Increases in CD4 from Baseline week baseline 8 12 16 24 n-1/2 17/16 17/16 16/16 14/16 9/12 group 1 177 +100 +130 +105 +175 group 2 134 +75 +80 +80 +100
CD8. For the immediate-group 1 (baseline=1027), there was a median cell increase from baseline of about 150 at week 8, 100 cells decrease below baseline at week 16, and back to about a 200 increase above baseline at week 24; for the delayed-group 2 (baseline= 927), the median increase from baseline was about 200 at week 8, a 50 cell increase above baseline at week 16; at week 24, the CD8 was about equal to the baseline.
Table 9- Median Changes in CD8 week baseline 8 16 24 n-1/2 17/16 17/16 14/16 9/12 group 1 1,027 +150 -100 +200 group 2 927 +200 +50 even
Plasma Viral Load. During the initial 4 weeks of therapy, the reduction in viral RNA appears to decline slightly more steeply and quickly for the immediate group than the delayed group; however, at week 4 (AZT/3TC is added at week 3) the median decline from baseline appears about equal for both groups at about 2.2 log. At weeks 8 and 12 (2.5 and 2.6 vs 2.6 and 2.75), the reduction in RNA is slightly more for the delayed group than for the immediate group; but, by week 16 both groups have pulled to about even in their median reduction from baseline in viral load (about 2.8 log for both groups); at week 24, both groups appear to have about equal reductions in viral load of about 2.8 log.
Table 10- Median Reductions in Viral Load week baseline 2 4 12 16 24 n-1/2 17/16 - 16/16 16/16 14/16 10/10 group 1 187,000 1.9log 2.2 2.6 2.8 2.8 group 2 235,000 1.75 2.2 2.8 2.8 2.8
The CD4, CD8 and viral load numbers (including those in the tables) are based upon estimations of line graphs, and therefore are approximations.
Proportion with RNA Below Detectability. For those study participants who remained on full doses of study medications (some study participants discontinued or interrupted therapy), 100% in group 1 (immediate) were below detectability (the Roche Amplicor test was used with a median lower level of detection of 238 copies/ml) at week 16; about 85% of those in group 2 (delayed) were undetectable at week 16; at week 24 100% of both groups were below the limit of detection.
Adverse Events and Withdrawals. A total of 8 study participants (24%) withdrew from study (5 were in immediate-group 1, and 3 were in delayed-group 2). Of the 5 group 1 individuals who withdrew, one withdrawal each occurred in weeks 5, 8, 12, and 20.Of the 3 group 2 individuals who withdrew, one each occurred at weeks 13, 16, and 24. The frequency of occurrence of adverse events given as reason for withdrawal: nausea and/or vomiting- 7; asthenia or malaise- 5; diarrhea- 3; abdominal pain- 2; dizziness- 1; night sweats- 1; palpitations- 1; some individuals complained of multiple adverse events as reasons for withdrawal.
Dr. Danner said, the results obtained to date do not point to a difference in antiretroviral potential between the two groups over the first three weeks; also he said, the incomplete reduction in viral load seen after 3 weeks (when compared to the reduction seen after 16 weeks) is not due to lack of potency, nor to rapidly developing resistance. He reported, one patient had mutations at 41 and 215, but was still undetectable; and, another patient had a V82A mutation after a few weeks, but was also undetectable. At baseline, two patients had A71T mutations and another had an A71V mutation.
Lymphoid Tissue. For each of the six participants who received tonsillar biopsies, investigators have baseline and six month values. Investigators said, 90% of a tonsillar biopsy consists of lymphoid tissue (Haase et al, Science, in press 1996); and, tonsillar biopsy, under local anasthesia is a safe and simple procedure. The tissue RNA load was measured with the Chiron ultra-sensitive bDNA test. The lower limit of detection of the test is 500 copies; this calculates to 30,000 copies per gram of tissues (or 30 copies per mg of tissue) and is 1.84 log. Notermans reported that by week 24, in all of the six patients, the tissue RNA was below the limit of detection of the test (500 copies).
Notermans requested that standards for anti-retroviral therapy be reset to include reducing HIV RNA levels in the lymphoid tissue in addition to reduction in the peripheral blood. He continued: "we need to follow-up to see how sustained the suppression is; and, we need to know other things, such as what happens to the level of pro-viral DNA in the lymphoid tissue. Even if we manage to suppress the virus strong and long enough, is reconstruction of the immune system possible"?
Commentary. Although the lymph tissue load was below 500 copies, residual virus may still be present and replicating. We don't yet understand the implications. Other researchers present at this meeting, said more refined methodology need to be used; a more refined methodology may yield a more definitive understanding of virus activity in lymph tissue. A goal is to be able to correlate virus activity in lymph tissue with virus activity in plasma (blood circulation). If a correlation can be established, it may not be necessary to measure viral burden in lymph tissue. There is controversy about pro-viral DNA. If present, some believe it may be defective and not significant, while others do not agree and think the presence of pro-viral DNA is important.
back to drug development
Last modified 8/20/96
copyright © 1996 natap