Effect of foscarnet therapy on human immunodeficiency virus p24 antigen levels in AIDS patients with cytomegalovirus retinitis

Circulating human immunodeficiency virus (HIV) p24 antigen levels were measured in 22 AIDS patients who had detectable serum antigen at baseline after induction and maintenance therapy of foscarnet for cytomegalovirus retinitis in phase I/II multicenter trials. The HIV p24 antigen levels decreased from a baseline value of 199 +/- 236 (mean +/- SD) and 140 pg/mL (median) to 106 +/- 218 and 28 pg/mL after 14 days of foscarnet induction therapy (60 mg/kg every 8 h). During chronic foscarnet maintenance, there was a sustained decrease in mean HIV p24 antigen levels below pre-foscarnet therapy baseline concentrations for a median of 16 weeks after foscarnet induction. These results provide evidence for a sustained clinical antiretroviral effect of chronic foscarnet maintenance therapy, consistent with a recent report that foscarnet-treated AIDS patients live longer than ganciclovir-treated patients.

In vivo additive antiretroviral effect of combined zidovudine and foscarnet therapy for human immunodeficiency virus infection (ACTG Protocol 053)

Zidovudine and foscarnet each have antiretroviral activity against human immunodeficiency virus (HIV) and, when combined in vitro, inhibit HIV replication in an additive or synergistic fashion. To determine if an in vivo additive or synergistic antiretroviral effect might result from combined therapy, six symptomatic HIV-infected patients were studied who had persistently quantifiable serum HIV p24 antigen despite 9-27 weeks of full-dose oral zidovudine therapy (1200 mg/day). These patients were given intravenous foscarnet (30 mg/kg every 8h) for 2 weeks with continued oral zidovudine for 14 days, followed by zidovudine alone for 6 months. Serum p24 antigen concentrations decreased in all six patients during the period of combined therapy by a mean 53% (P = .005). Subsequently, serum p24 antigen levels rose to the baseline value in four patients after 4-14 weeks. As predicted from in vitro studies, combined treatment with zidovudine and foscarnet resulted in an additive in vivo effect, but the effect was transient.

Foscarnet-induced hypocalcemia and effects of foscarnet on calcium metabolism

Foscarnet (trisodium phosphonoformate), an investigational pyrophosphate analog increasingly used to treat refractory cytomegalovirus retinitis and mucocutaneous herpes simplex virus infections in immunocompromised patients, has been reported to cause abnormalities in serum calcium and phosphate, including cases of fatal hypocalcemia. To further elucidate the magnitude and mechanism of these abnormalities in humans treated with foscarnet for opportunistic herpes virus infections, we analyzed anaerobic serum specimens and 24-h urine samples before and after single and multiple doses of iv foscarnet and performed a series of in vitro experiments with normal human serum and plasma. Plasma ionized calcium concentrations acutely decreased by a mean 0.17 mmol/L in the 6 individuals who received a 90 mg/kg dose of foscarnet and by a mean 0.28 mmol/L in the 11 individuals who received a 120 mg/kg dose (P = 0.016, 90 vs. 120 mg/kg dose). Results of in vitro experiments showed a highly significant inverse linear relationship between foscarnet and ionized calcium concentrations, but no correlation between foscarnet and total calcium or phosphate concentration. Dialysis experiments suggested that the complexing of foscarnet with ionized calcium could be a cause of this ionized hypocalcemia. Physicians must be aware of this phenomenon and should measure serum ionized calcium during foscarnet therapy (preferably at the end of a foscarnet infusion) whenever neurological or cardiological abnormalities occur.

A pilot study of low-dose zidovudine in human immunodeficiency virus infection

BACKGROUND

Zidovudine delays the progression of human immunodeficiency virus (HIV) infection but is associated with hematologic toxicity at high doses. Regimens are needed that preserve or enhance efficacy and reduce toxicity. Acyclovir has been reported to potentiate the effect of zidovudine on HIV in vitro.

METHODS

We conducted a Phase II open-label, dose-escalating trial to evaluate the clinical and antiviral effects of zidovudine at low (300 mg daily, 28 subjects), medium (600 mg, 24 subjects), and high (1500 mg, 15 subjects) doses, either with or without acyclovir (4.8 g) by random assignment. The subjects had the acquired immunodeficiency syndrome (AIDS)-related complex, but not AIDS. All of them had either HIV p24 antigenemia or plasma viremia and CD4-lymphocyte counts of 200 to 500 per cubic millimeter when they began treatment.

RESULTS

Performance scores and fatigue improved the most in the low- and medium-dose zidovudine groups (both P less than or equal to 0.025). Those assigned to low-dose zidovudine gained the most weight and had the greatest improvement in the mean CD4-lymphocyte count (from 321 per cubic millimeter at base line to 412 per cubic millimeter after 12 weeks, P = 0.01). The proportion of subjects in whom HIV antigenemia resolved, the decrease in the level of antigenemia, and the reduction in the plasma virus titers were similar at all three doses. Subjects assigned to receive the low or medium dose who subsequently crossed over to the 1500-mg dose (n = 19) did not have an increase in CD4-cell counts or a decline in levels of HIV antigen, but they did have dose-related toxicity. The addition of acyclovir to zidovudine was well tolerated, but it did not enhance any of zidovudine's antiretroviral effects.

CONCLUSIONS

In this pilot study a very low dose of zidovudine (300 mg) had clinical and virologic effects similar to those of higher daily doses (600 and 1500 mg). The minimal effective dose of zidovudine for the treatment of HIV infection has yet to be determined, and further studies of very low daily doses are warranted.

Prolonged zidovudine therapy in patients with AIDS and advanced AIDS-related complex. AZT Collaborative Working Group

We examined the long-term safety and efficacy of zidovudine therapy in 229 subjects with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex who previously participated in a placebo-controlled study of zidovudine. One hundred two placebo recipients (delayed treatment group) and 127 zidovudine recipients (original treatment group) were followed up while receiving zidovudine therapy for a mean of 21 months. Survival rates for the original treatment group were 84.5% and 57.6% at 12 and 21 months, respectively; for the delayed treatment group, 78.8% and 64.6% at 12 and 21 months, respectively, and 78.8% and 47.5% at 12 and 21 months, respectively, for 77 subjects with AIDS and 93.0% and 71.8%, respectively, for 50 subjects with AIDS-related complex in the original treatment group. Adverse reactions decreased over time and newly observed toxic reactions were unusual. The clinical course of these subjects suggests continued survival benefits with long-term zidovudine therapy.

Detection of cytomegalovirus DNA in peripheral blood of patients infected with human immunodeficiency virus

Detection of cytomegalovirus (CMV) DNA can be facilitated by the polymerase chain reaction (PCR), an in vitro gene amplification technique. Twenty-eight CMV tissue culture isolates were examined by amplification of two separate CMV genes. All were found to contain CMV, although two of the isolates were positive for only one of the two genes. No detectable amplification occurred with human genomic or other viral DNA controls. The amplification products from as few as one CMV plaque-forming unit could be detected after the PCR. CMV DNA was detected in the blood of 14 of 27 patients with AIDS and one of six patients who were infected with human immunodeficiency virus but who did not have AIDS. Normal CMV-seropositive or -seronegative individuals did not have CMV DNA detected in their blood. The CMV PCR was more sensitive than the standard culture assay, can be completed in one to two days, uses only 20 microL of blood, and may be useful for rapidly detecting CMV in clinical specimens.

Cytomegalovirus retinitis and response to therapy with ganciclovir

A 15-month prospective study of 109 patients with the acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC) was conducted. Cytomegalovirus (CMV) retinitis developed in 18 of these patients; they were treated with ganciclovir. Five other patients with CMV retinitis who were not part of the prospective study were also treated with ganciclovir. CMV retinitis frequently involved the peripheral retina. All 23 patients treated with ganciclovir showed clinical regression of retinitis, although breakthrough recurrence of CMV retinitis occurred in seven patients (30.4%) while on maintenance therapy with ganciclovir. During treatment, neutropenia (less than 1000 leukocytes/mm3) developed in three patients (13%). Ganciclovir is an effective means of therapy for CMV retinitis, but it must be given chronically to prevent reactivation. Breakthrough recurrences while on maintenance therapy are not uncommon, but can be successfully treated with more aggressive treatment with ganciclovir. In addition, the prognosis for survival of AIDS patients being treated with ganciclovir is improved when compared with that of untreated patients.