Virological efficacy and plasma drug concentrations of nelfinavir plus saquinavir as salvage therapy in HIV-infected patients refractory to standard triple therapy.

Therapeutic options are limited for patients refractory to triple therapy with two reverse transcriptase inhibitors and one protease inhibitor. Preliminary results showing favorable effects of protease inhibitor combination therapy with nelfinavir and saquinavir due to inhibition of metabolism by cytochrome P450 (CYP450) prompted us to study this combination. - Thirteen patients with incomplete suppression of plasma HIV-RNA were enrolled and treatment was started with nelfinavir 750 mg tid and saquinavir 400 mg bid. Saquinavir-dosage was escalated in weekly intervals to 400 mg tid and 600 mg tid, respectively. All doses were given with food, and plasma levels of saquinavir and nelfinavir were assessed 4 hours post-dosing after 1, 2, 3, 4 and 8 weeks. Treatment was considered virologically efficacious if HIV-viral load was reduced by at least 0.5 log10 from baseline. - Double protease inhibitor-treatment with nelfinavir and saquinavir was virologically efficacious in 5/13 (39%) patients after 4 weeks but only in 4/13 (31%) patients after 8 and 1/13 (8%) after 16 and 24 weeks, respectively. No statistical difference in plasma concentrations was observed when saquinavir was administered in increasing doses of 400 mg bid, 400 mg tid or 600 mg tid in combination with nelfinavir. 5/13 (39%) patients developed diarrhea (>4/d), no other serious side-effects were observed. By eight weeks, the mean CD4 count for all patients was significantly higher when compared to baseline. - In patients refractory to standard triple therapy the combination of nelfinavir and saquinavir showed significant elevation of CD4-count, but only short term virological efficacy in a minority of patients. Plasma concentrations of saquinavir could not be increased by weekly dose escalation of the drug from 400 mg bid to 600 mg tid. Saquinavir drug concentrations of 600 mg saquinavir tid and nelfinavir showed rather non-significant lower values when compared to historical controls treated with a double-dose 1200 mg saquinavir tid regimen alone. We conclude that in these patients the combination of nelfinavir plus saquinavir has no advantage in terms of increasing bioavailibility of saquinavir or virological efficacy. During short observation time a beneficial effect on CD4-count was observed.