PI-containing Regimen Research Articles

New antiretroviral drugs and approaches to HIV treatment.

New antiretroviral drugs and approaches to HIV treatment.

Open-Label Study of a Twice-Daily Indinavir 800-mg/Ritonavir 200-mg Regimen in HIV-Infected Adults Failing a Protease Inhibitor Regimen

There is no standard treatment of HIV-infected patients who fail protease inhibitor (PI)-containing antiretroviral therapy. This open-label, noncomparative 24-week study with a 24-week extension evaluated the efficacy, safety, and tolerability of twice-daily indinavir/ritonavir 800/200 mg plus 2 nucleoside reverse transcriptase inhibitors (NRTIs) in this population. Presented here are the results of the 24-week study. Patients were HIV-infected adults who had prior viral RNA (vRNA) suppression (<400 copies/mL), subsequent failure (> or =400 and < or =100,000 copies/mL) on antiretroviral therapy, and at least one new NRTI available for treatment. The proportions of patients achieving plasma vRNA <400 and <50 copies/mL were analyzed with data as observed (DAO) and intention-to-treat (ITT) models using generalized estimating equations (GEE) or counting noncompleters as failures (NC = F). Mean changes from baseline in vRNA and CD4 cell count were evaluated using DAO and an ITT mixed-model approach. Sixty-three patients (87% male) with a mean age of 42 years and mean baseline vRNA and CD4 cell counts of 3.8 log(10) copies/mL and 360 cells/mm(3), respectively, were enrolled. The proportion (95% confidence interval) of patients achieving vRNA <400 and <50 copies/mL at week 24 were 76% (61%, 87%) and 50% (35%, 65%) for DAO, 64% (50%, 75%) and 43% (30%, 56%) for GEE, and 56% (43%, 68%) and 37% (25%, 50%) for NC = F, respectively. At Week 24, baseline vRNA decreased by >1.0 log(10) copies/mL and CD4 cell counts increased by approximately 90 cells/mm(3). Three patients (5%) experienced serious drug-related adverse events. Seven patients (11%) discontinued treatment due to clinical or laboratory adverse events. In this study, the enhanced, twice-daily regimen of indinavir/ritonavir 800/200 mg plus 2 NRTIs provided suppression of HIV in many patients who had failed a PI-containing regimen and was generally well tolerated.

Long-term outcomes among antiretroviral-naive human immunodeficiency virus-infected patients with small increases in CD4+ cell counts after successful virologic suppression.

To evaluate the frequency and predictive factors of discordant immune response, we performed a prospective cohort study of 288 antiretroviral-naive human immunodeficiency virus (HIV)-infected patients who initiated highly active antiretroviral therapy (HAART) and maintained complete virus suppression for > or =24 months. The median CD4+ cell count was 186x10(6) cells/L, and the median HIV RNA level was 5 log(10) copies/mL. After 24 months of therapy, 42 (16.5%) of 255 patients had a median CD4+ cell count increase of <100x10(6) cells/L. By logistic regression analysis, previous injection drug use was associated with a CD4+ cell count increase of <100x10(6) cells/L (risk ratio [RR], 2.326; 95% confidence interval [CI], 1.077-5.023; P=.032); inclusion of a protease inhibitor (PI) in the HAART regimen reduced the risk of poor immunologic recovery (RR, 0.160; 95% CI, 0.061-0.417; P<.001). Failure of the CD4+ cell count to increase was relatively common among antiretroviral-naive patients in the year after the initiation of HAART and the achievement of complete virus suppression. PI-containing regimens provided better immunologic response.

In vitro and in vivo modulation of MDR1/P-glycoprotein in HIV-infected patients administered highly active antiretroviral therapy and liposomal doxorubicin.

P-glycoprotein (P-gp) transports a wide range of structurally unrelated drugs, such as HIV protease inhibitors (PIs) and cytotoxic compounds such as anthracyclines. Because modification of P-gp phenotype and function is an important underlying mechanism of drug interactions, the current study was conducted in order to evaluate whether highly active antiretroviral therapy (HAART), HIV plasma viral load (VL), or cancer chemotherapy may induce in vivo changes of P-gp phenotype in peripheral blood mononuclear cells (PBMCs) from HIV-infected treatment-naive and -experienced subjects at different stages of HIV infection and/or disease, including patients with HIV-associated Kaposi sarcoma (KS). Our results show that neither HAART nor HIV VL, nor the stage of HIV infection and/or disease, significantly alter P-gp expression on PBMCs. In particular, surface P-gp expression is expressed at low levels by T-cell subsets, B cells, and NK cells, whereas almost all monocytes are double positive and these results are not modified by HIV PI-containing regimens. By contrast, a significant phenotype modification is detected in PBMCs from AIDS/KS patients after challenge with the liposomal formulation of the anthracycline doxorubicin (L-DOX) with the higher expression reached 24 hours after the end of the drug infusion. In addition, accumulation of L-DOX is unaffected by P-gp-mediated drug efflux as documented by in vitro experiments, in sharp contrast to the kinetic of free DOX, based on HIV PI blockade experiments. Finally, P-gp expression was found in KS spindle cells from HIV-infected treatment-naive AIDS/KS patients. We conclude that P-gp phenotype in PBMCs and specific subsets is not altered by HAART and/or HIV, whereas a significant increase is induced by specific anticancer drugs such as L-DOX. Moreover, HIV PIs possess an inhibitory effect on P-gp function that may improve DOX sensitivity in KS spindle cells.

Low risk of treatment failure after substitution of nevirapine for protease inhibitors among human immunodeficiency virus-infected patients with virus suppression.

There is little information about the risk of treatment failure after a switch from human immunodeficiency virus (HIV) protease inhibitors (PIs) to nevirapine (Nvp) for patients with successful virus suppression. This study compared the 1-year risk of treatment failure for patients switching from a first PI-containing antiretroviral regimen to Nvp (Nvp group) with the risk for patients switching to second-line PIs (PI group) in the ATHENA (AIDS Therapy Evaluation, The Netherlands) study cohort (n=2470) whose HIV-1 RNA loads were < or = 500 copies/mL. Treatment failure was defined as measurement of HIV-1 RNA loads >500 twice or >10,000 copies/mL once or discontinuation of treatment for any reason. There were 446 eligible patients, 125 in the Nvp group and 321 in the PI group. The risk of treatment failure in the Nvp group, after data were adjusted for other risk factors, was 5-fold (95% confidence interval, 0.1-0.4) lower than the risk in the PI group, primarily because the discontinuation rate was lower. In patients with virus suppression, a switch to Nvp is more likely than a switch to second-line PIs to result in sustained virus suppression and maintenance of the new regimen.

Immunologic Reconstitution After 1 Year of Highly Active Antiretroviral Therapy, With or Without Protease Inhibitors

Objectives: To assess the effectiveness of two triple antiretroviral combinations (2 nucleoside reverse transcriptase inhibitors [NRTIs] + 1 protease inhibitors [PI] vs. 2 NRTIs + 1 nonnucleoside reverse transcriptase inhibitor [NNRTI]) to correct T-cell subsets abnormalities and to restore immune functions in asymptomatic antiretroviralnaive HIV-1-infected patients with a baseline CD4 T-cell counts >500/mm3 and plasma viral load >5000 copies/mL. Design and Methods: Twenty randomized patients from 2 cohort studies receiving either stavudine (d4T) + lamivudine (3TC) + indinavir (n = 9), or d4T + didanosine (ddI) + nevirapine (NVP) (n = 11) were studied. Viral load, T-cell subsets and T-cell functions were analyzed at baseline and after 1 year of treatment. Results: After 1 year of follow-up, the PI regimen was significantly more effective in reducing plasma and lymphoid tissue VL to undetectable levels. A significant increase in CD4+ T cells was observed in patients treated with PI (p = .0007) compared with those treated with NVP. Percentages of CD8+ T-cells and of activated CD8+ T-cells (CD38+ and DR+ as well as memory CD45RO+) decreased in all patients. An increase of the CD28+ subset of CD8+ T-cells also occurred in both groups of treatment. Naive T cells were maintained in the CD4+ subset and augmented in the CD8+ subset in all patients. In both PI and NVP groups, memory CD4+ T-cells increased significantly (p = .03). Peripheral blood mononuclear cell responsiveness to polyclonal stimuli and to tetanus toxoid and cytomegalovirus (CMV) antigen was similar in both groups of treatment. HIV-infected patients treated for 1 year with both triple combinations lacked significant T-cell responsiveness to HIV-1 proteins. Conclusions: These data suggest that immune reconstitution achieved after 1 year of therapy with PI-containing or PI-sparing regimens is similar, despite the higher effectiveness of PI-containing regimens in reducing viral load. Additional therapeutic approaches should be designed to restore HIV-1-specific responses.

Determinants of recurrent toxicity-driven switches of highly active antiretroviral therapy. The ATHENA cohort.

Toxicity is the most important reason for premature switching of highly active antiretroviral therapy (HAART). In order to optimize the benefit-risk ratio of HAART, guidelines for toxicity management are needed. An observational cohort study to estimate the incidence and identify determinants of toxicity-driven switches on second-line HAART after having switched first-line HAART despite successful viral suppression. Patients were selected from those in the ATHENA cohort (n = 2470) who switched the initial HIV protease inhibitor (PI)-containing HAART while plasma HIV-1 RNA was <or= 500 copies/ml (n = 775). One-year cumulative incidences of subsequent toxicity-driven switches and adjusted relative risks (RR) for potential determinants were calculated. The 1-year cumulative incidence of toxicity-driven switches of the second regimen was 24% [95% confidence interval (CI), 21-28], mostly because of gastrointestinal toxicity and neuropathy. Those who had switched from first HAART because of toxicity were at an increased risk of a recurrent toxicity-driven switch (RR, 2.5; 95% CI, 1.7-3.5). Switching from PI to nevirapine while continuing the other antiretroviral drugs was more protective against a subsequent switch because of further toxicity than changing to another PI-containing regimen (RR, 0.2; 95% CI, 0.1-0.6). As for first-line HAART, toxicity is responsible for the majority of switches during second-line HAART. Prior switching for toxicity increased the risk of having to switch the subsequent regimen for toxicity, but this risk is reduced when switching to nevirapine rather than to an alternative PI. The latter should be taken into account when designing toxicity-management guidelines.

Two-Year Outcome of a Multidrug Regimen in Patients Who Did Not Respond to a Protease Inhibitor Regimen

Summary: In most studies, people who have not responded virologically to a protease inhibitor (PI)-containing regimen have tended to experience poor virologic responses to subsequent regimens. We describe the 2-year viral load, CD4 count, and clinical outcome of a multidrug regimen used in 60 people who had not responded virologically to a PI-containing regimen. At baseline, median CD4 count was 126/mm3 (nadir 30/mm3) and median viral load was 320,000 copies/mL. A median of five antiretroviral drugs had previously been used, of which a median of two were PIs. Of these patients, 16% had previously used another nonnucleoside reverse transcriptase inhibitor besides efavirenz. The multidrug regimen (median 5 drugs) started most commonly included efavirenz (100%), at least one PI (92%, usually indinavir/ritonavir), didanosine (78%), and hydroxyurea (74%). At year 2, 5 patients had died and 5 had no measure available. Nine patients developed a new AIDS event and 10 patients were known to have stopped all antiretroviral therapy. Thirty-one patients (52% of the whole group, 72% of those remaining on therapy with viral load value available) had viral load <50 copies/mL. Thus, a substantial proportion of patients who had failed to respond virologically to PI-containing regimens can achieve profound and sustained virologic suppression with a multidrug regimen.

Protease inhibitors and erectile dysfunction.

Increasing numbers of HIV-positive men receiving protease inhibitors (PI) complain of erectile dysfunction (ED). Through the analysis of 334 HIV-1-infected male outpatients, this study shows homosexuality, CD4 cell count, viral load, and indinavir treatment to be independent variables predictive of ED. Furthermore, a neuropathy of the sacral region was detected in 12 patients with ED who underwent diagnostic investigations. For the first time, a PI-containing regimen has been associated with peripheral neuropathy causing ED.

DPC 681 and DPC 684: potent, selective inhibitors of human immunodeficiency virus protease active against clinically relevant mutant variants.

Human immunodeficiency virus (HIV) protease inhibitors (PIs) are important components of many highly active antiretroviral therapy regimens. However, development of phenotypic and/or genotypic resistance can occur, including cross-resistance to other PIs. Development of resistance takes place because trough levels of free drug are inadequate to suppress preexisting resistant mutant variants and/or to inhibit de novo-generated resistant mutant variants. There is thus a need for new PIs, which are more potent against mutant variants of HIV and show higher levels of free drug at the trough. We have optimized a series of substituted sulfonamides and evaluated the inhibitors against laboratory strains and clinical isolates of HIV type 1 (HIV-1), including viruses with mutations in the protease gene. In addition, serum protein binding was determined to estimate total drug requirements for 90% suppression of virus replication (plasma IC(90)). Two compounds resulting from our studies, designated DPC 681 and DPC 684, are potent and selective inhibitors of HIV protease with IC(90)s for wild-type HIV-1 of 4 to 40 nM. DPC 681 and DPC 684 showed no loss in potency toward recombinant mutant HIVs with the D30N mutation and a fivefold or smaller loss in potency toward mutant variants with three to five amino acid substitutions. A panel of chimeric viruses constructed from clinical samples from patients who failed PI-containing regimens and containing 5 to 11 mutations, including positions 10, 32, 46, 47, 50, 54, 63, 71, 82, 84, and 90 had mean IC(50) values of <20 nM for DPC 681 and DPC 681, respectively. In contrast, marketed PIs had mean IC(50) values ranging from 200 nM (amprenavir) to >900 nM (nelfinavir).

Hepatitis C and PIs.

In a large, retrospective analysis of HIV/HCV-coinfected patients, treatment with PI-containing regimens was associated with lower fibrosis scores and a slower progression to cirrhosis.

Long-term clinical benefit after highly active antiretroviral therapy in advanced HIV-1 infection, even in patients without immune reconstitution

Our objective was to assess, in the clinical setting, the predictors of immune reconstitution (IR) and its relation with long-term clinical benefit, in HIV patients with advanced disease after highly active antiretroviral therapy (HAART) through an observational study. A retrospective cohort study in a clinical setting of 383 consecutive adult patients with advanced HIV infection (CD4+ cells <200/mm(3) at baseline), starting their first protease inhibitor (PI)-containing regimen was observed. Immune reconstitution was defined as CD4 count >200 cells/mm(3) and an increase > or =100 cells from baseline, anytime since starting HAART. Clinical benefit was defined as decreased mortality and reduction in AIDS-defining events, AIDS-related complex (ARC) events, major infections and hospitalization (days spent in hospital). During a mean follow-up of 808 days, 261 patients (68.1%) achieved IR. About 50% of these patients reached this result within one year after starting HAART. In multivariate analysis, predictors of immune recovery were sex (female) and baseline CD4 count higher than 50 cells/mm(3). The group of patients with IR had greater clinical benefit with lower mortality, fewer AIDS-defining events, shorter lengths of stay in hospital, fewer ARC events and fewer major infections during all the follow-up (P < 0.0001, tests for trends). However, although they did less remarkably than the first group of patients, even those patients who did not achieve IR experienced a significant decrease in the incidence of all the above events, as compared with the first and sometimes the second trimester after starting their HIV therapy. About 70% of HIV patients with advanced disease achieved IR after starting HAART. Such a benefit is a time-dependent effect and may even take more than 2 years to occur. Predictors of IR were sex (female) and higher baseline CD4 count (>50 cells/mm(3)). The patients who achieved immune recovery performed clinically better than patients who did not. Also the patients who failed to gain such a strong immunological recovery experienced a long-term clinical benefit. This suggests that PI-containing regimens, in advanced HIV disease, may produce a significant clinical benefit, at least temporary, even for patients who do not achieve a substantial immune response.

Efavirenz as a Substitute for Protease Inhibitors in HIV-1–Infected Patients With Undetectable Plasma Viral Load on HAART: A Median Follow-Up of 64 Weeks

Summary: We investigated, in a prospective cohort follow-up study, whether substituting efavirenz (EFV) for protease inhibitors (PIs) could be safe in HIV-infected patients with optimal viral suppression achieved on PI-containing regimens. In patients with undetectable plasma viral load (pVL) <50 copies/ml who were naive to therapy with nonnucleoside reverse transcriptase inhibitors (NNRTIs), PIs were replaced by EFV whereas associated nucleoside analogs (NAs) were retained. 62 patients were enrolled. Median follow-up on EFV was 64 weeks (2-88 weeks). Side effects due to EFV occurred in 48 patients. Two patients experienced a high level viral rebound due to diminished compliance; 55 (88.7%) maintained a pVL <50 copies/ml; 3 showed one episode of viremia (52-89 copies/ml); 2 stopped EFV before any VL control. Mean CD4 cell count did not change significantly. One AIDS patient experienced a single cutaneous recurrence of Kaposi's sarcoma after 40 weeks on EFV. Replacing PI with EFV in patients with optimal pVL suppression appears to be safe both virologically and immunologically.

Efavirenz as a Substitute for Protease Inhibitors in HIV-1–Infected Patients With Undetectable Plasma Viral Load on HAART: A Median Follow-Up of 64 Weeks

We investigated, in a prospective cohort follow-up study, whether substituting efavirenz (EFV) for protease inhibitors (PIs) could be safe in HIV-infected patients with optimal viral suppression achieved on PI-containing regimens. In patients with undetectable plasma viral load (pVL) <50 copies/ml who were naive to therapy with nonnucleoside reverse transcriptase inhibitors (NNRTIs), PIs were replaced by EFV whereas associated nucleoside analogs (NAs) were retained. 62 patients were enrolled. Median follow-up on EFV was 64 weeks (2-88 weeks). Side effects due to EFV occurred in 48 patients. Two patients experienced a high level viral rebound due to diminished compliance; 55 (88.7%) maintained a pVL <50 copies/ml; 3 showed one episode of viremia (52-89 copies/ml); 2 stopped EFV before any VL control. Mean CD4 cell count did not change significantly. One AIDS patient experienced a single cutaneous recurrence of Kaposi's sarcoma after 40 weeks on EFV. Replacing PI with EFV in patients with optimal pVL suppression appears to be safe both virologically and immunologically.

Dyslipidaemia in HIV-infected patients: association with adherence to potent antiretroviral therapy

Metabolic complications are being increasingly recognized among HIV-infected patients treated with potent combination antiretroviral therapies. We sought to assess the association of dyslipidaemia with adherence to protease inhibitor (PI) therapy and with the markers of clinical response to antiretroviral therapy (CD4 count, HIV RNA viral level) through a prospective, cross-sectional cohort study. Fifty-six HIV-infected patients who were already on, or who were started on PI-containing antiretroviral therapy were monitored for the development of dyslipidaemias. Therapy with PI-containing antiretroviral therapy was significantly associated with elevated serum triglyceride level (>250 mg/dl) (52% vs 8%, P=0.001). Patients with an adherence rate of at least 80% to a PI-containing regimen were significantly more likely to have elevated low density lipoprotein (LDL) cholesterol level as compared to patients with an adherence rate of <80% (79% vs 26%, P=0.03). Patients with an adherence rate of at least 80% to a PI-containing regimen were also significantly more likely to have severe hypertriglyceridaemia (>800 mg/dl) as compared to patients with an adherence rate of <80% (21% vs 4%, P=0.04). Viral load at the last study visit did not correlate with total cholesterol (r=-0.39, P=0.30), LDL cholesterol (r=0.57, P=0.30), or triglyceride level (r=0.55, P=0.20). However, there was a significant correlation between the last viral load and high density lipoprotein (HDL) cholesterol (r=0.79, P=0.035), i.e. lower viral load was associated with higher HDL cholesterol level. In conclusion, dyslipidaemia in patients with HIV infection was significantly associated with adherence to PI-containing antiretroviral therapy. Patients who are adherent to PI-containing regimens at least 80% of the time warrant close monitoring for the development of dyslipidaemia.

Predictors of protease inhibitor-associated adverse events

Risk factors in the development of adverse reactions in HIV-1-infected patients treated with highly active antiretroviral therapy (HAART) containing protease inhibitors are poorly understood. To identify predictors of protease inhibitor-associated adverse events, we are conducting a prospective, cohort, multicenter study on HIV-positive patients starting treatment with at least one protease inhibitor. Rate ratios (RR) of adverse events were calculated, and logistic regression was used to adjust simultaneously for the potentially confounding effects of selected variables, according to the Cox model. A total of 1477 patients have been enrolled up to April 2000, having an average age of 37.1 years (SD ± 8.1); 1066 (72.2%) were male. Where risk factors for HIV infection are concerned, the distribution was as follows: 48.1% intravenous drug users, 31.6% heterosexual contacts, 16.2% homosexual males and 0.7% blood transfusion. Average CD4+ lymphocyte count at enrollment was 265 cells/mmc (SD ± 201). Average follow-up time is equal to 17.8 months (range 1–32). The risk of developing adverse reactions is significantly increased in female patients, older patients, hemophiliac subjects and in subjects with hepatitis. Patients treated with ritonavir, the association ritonavir-saquinavir HGC, stavudine and efavirenz have significantly increased incidence of adverse reactions in PI-containing regimens; conversely, saquinavir HGC, zidovudine and lamivudine use was associated with a lower risk of developing adverse reactions.

Usefulness of route of transmission, absolute CD8+ T-cell counts, and levels of serum tumor necrosis factor alpha as predictors of survival of HIV-1-infected patients with very low CD4 + T-cell counts.

Potential cofactors of survival in HIV-1-infected patients with CD4+ T-cell counts of < or = 100 cells/microl were investigated. All 132 patients with CD4+ T-cell counts of < or = 100 cells/microl were selected from 416 patients included in an antiretroviral therapy cohort (1989-1999). Fifty of 54 deaths were due to AIDS. There were significant associations (P<0.05) between survival and CD8+ T-cell counts, clinical AIDS stage, risk group, and antiretroviral drug regimen after baseline, but only the use of protease inhibitors had an independent effect on survival (hazard ratio [HR], 0.096; 95% confidence interval [95%CI], 0.094-0.097). A substudy restricted to the cohort of 108 patients never exposed to PIs detected independent associations between survival and CD8+ T-cell counts (P=0.0016), experience with antiretroviral therapy before baseline (HR, 2.52; 95%CI, 1.31-4.82), sexual risk group for HIV infection (HR, 3.7; 95%CI, 1.92-7.12), and levels of serum tumor necrosis factor alpha (P=0.02). This study confirms that the use of PI-containing antiretroviral regimens strongly predicts survival of HIV-1-infected patients with very low CD4+ T-cell counts. When the study was restricted to patients never exposed to PIs, the parenteral route of disease transmission, high absolute CD8 + T-cell counts, and low serum levels of tumor necrosis factor alpha were independent predictors of survival in extremely advanced HIV-1 disease.

Safety profile and tolerability of amprenavir in patients enrolled in an early access program

Background: The amprenavir (APV) early or expanded access program was designed to provide open-label APV to patients who would potentially receive benefit beyond that expected from currently available protease inhibitors (PIs) and who were at risk of disease progression before the drug's expected time of regulatory approval. Objective: This study was conducted as part of an early access program to assess the safety profile and tolerability of APV in adults and children (≥4 years of age) who were either intolerant to or, in the opinion of the patient's physician, virologically failing a previous PI-containing antiretroviral regimen. Specific CD4 + cell count and viral load limits were not imposed by this early access protocol. Methods: This open-label, nonrandomized study was conducted at multiple sites throughout the United States. Adults received APV at a dosage of 1200 mg BID. Patients weighing <50 kg received APV at a dosage of 20 mg/kg BID for the solid formulation or 1.5 mL/kg BID for the liquid formulation. Results: A total of 489 physicians registered for this program; 364 (74.4%) enrolled patients. The safety population of 2217 patients (2048 males [92.4%] and 169 females [7.6%] aged 2 to 74 years) received APV for a median duration of 85 days (range, 2–218 days). Patients in the intent-to-treat population (n = 1427) had extensive experience with antiretroviral therapy. Drug-related treatment-emergent adverse events reported in > 3% of patients in the safety population were nausea in 279 patients (12.6%), diarrhea in 197 patients (8.9%), rash in 177 patients (8.0%), vomiting in 148 patients (6.7%), and fatigue in 89 patients (4.0%). Adverse events and laboratory test abnormalities were graded for severity on a scale of 1 to 4 in accordance with AIDS Clinical Trials Group guidelines. Grade 3 treatment-emergent abnormal laboratory values regardless of causality occurring in > 3% of patients were neutropenia in 69 of 1887 patients (3.7%; grade 3 toxicity = 500–749/mm 3) and elevated triglycerides in 80 of 1593 patients (5.0%; grade 3 toxicity = 751–1200 mg/dL). Most common grade 4 treatment-emergent laboratory abnormalities were elevated serum creatine phosphokinase levels in 36 of 1266 patients (2.8%; grade 4 = > 6 times upper normal limit), elevated triglycerides in 39 of 1593 patients (2.4%), and neutropenia in 41 of 1887 patients (2.2%). Conclusions: The results of this large cohort of patients support the data from the phase II/III clinical development program and suggest that APV has an acceptable safety profile and is generally well tolerated when used in combination with other antiretroviral drugs in a heavily treatment-experienced, heterogeneous patient population.

The use of and response to second-line protease inhibitor regimens: results from the EuroSIDA study

To describe the use of second line protease-inhibitor (PI) regimens across Europe and to determine factors associated with virological and immunological response. Analysis of data from 984 patients with a median follow-up of 21 months enrolled in EuroSIDA. Patients started their second PI-containing regimen at least 16 weeks after starting the first PI-containing regimen and with viral load > 1000 copies/ml. Virological response was defined as a viral load < 500 copies/ml and immunological response as an increase of 50 x 10(6)/l or more in CD4 lymphocyte count. The median CD4 cell count at starting the second PI was 171 x 10(6) cells/l; viral load was 4.45 log copies/ml. As a second PI regimen, 45% were using a dual PI, while of those on one PI, indinavir (42%) and nelfinavir (34%) were most common. In multivariate Cox models, a higher viral load at starting the second PI [relative hazard (RH), 0.67 per 1 log higher; 95% confidence interval (CI), 0.58-0.77; P < 0.0001) and a lower CD4 cell count (RH, 1.15 per 50% higher; 95% CI, 1.06-1.26; P = 0.0014) were associated with a reduced probability of virological response. Those who had achieved viral suppression on the first PI-regimen were more likely to respond to the second (RH, 1.65; 95% CI, 1.30-2.10; P < 0.0001) as were those who added one or two new nucleosides to their second PI. Patients who initiate a second PI regimen at lower viral load, higher CD4 cell count or who added new nucleosides tended to be more likely to achieve a viral load < 500 copies/ml. The roles of cross-resistance and adherence in response to second-line regimens needs further investigation.

Protease inhibitor-resistant HIV-1 from patients with preserved CD4 cell counts is cytopathic in activated CD4 T lymphocytes.

To evaluate CD4 T-cell cytopathicity of protease inhibitor (PI)-resistant isolates from patients with preserved CD4 cell counts after long-term virologic failure. PI-resistant primary isolates from 14 patients with stable or increasing CD4 T-cell counts despite long-term virologic failure during continuous combination therapy were examined. Replication and cytopathicity were assessed in activated peripheral blood mononuclear cell cultures in the presence and absence of PI using titered stocks of primary HIV-1 isolates and during initial viral isolation. Also studied were PI-sensitive isolates from four of these patients after therapy discontinuation and reversion to PI-sensitive virus and from seven antiretroviral drug-naive patients. Coreceptor use, syncytia-inducing (SI) phenotype and protease sequences were determined by standard methods. All isolates obtained during continued therapy showed genetic markers of PI resistance and decreased phenotypic susceptibility. PI-resistant SI isolates were highly to moderately cytopathic whereas non-syncytia-inducing isolates were moderately to weakly cytopathic. PI-susceptible and PI-resistant isolates obtained after discontinuation of therapy were equally cytopathic at similar replication levels. The cytopathicity of PI-resistant isolates was not altered by PI and was similar to that of isolates from untreated subjects. Primary isolates from patients showing virologic rebound without net CD4 T-cell loss during continued therapy are as cytopathic as PI-sensitive isolates with equivalent input infectious titer. As with PI-sensitive isolates, cytopathicity of PI-resistant viruses was determined primarily by coreceptor preference. These results suggest that the sustained immunologic response observed after failure of PI-containing regimens is not due to the emergence of PI-resistant strains that are intrinsically less cytopathic for activated peripheral CD4 lymphocytes.