Approved HIV Protease Inhibitor Research Articles

Nelfinavir and Lenalidomide/Dexamethasone in Patients with Lenalidomide-Refractory Multiple Myeloma. A Phase I/II Trial — SAKK 39/10

▪IntroductionNelfinavir (NFV) is an approved HIV protease inhibitor. In mammalian cells, NFV induces proteotoxic stress and activates the unfolded protein response (UPR) via an unknown mechanism. NFV in combination with bortezomib and dexamethasone (NeVd) is highly active in patients with advanced, proteasome inhibitor-refractory multiple myeloma (Driessen et al Blood 2016, 128(22), 487). We hypothesized that the addition of NFV to standard lenalidomide/dexamethasone (Rd) may overcome lenalidomide-resistance in myeloma patients (pts).MethodsThis multicenter, dose escalation phase I/II trial used a 3+3 design to identify the recommended dose of NFV. Pts having progressed during or within 60 days after termination of lenalidomide-containing therapy were eligible for this trial. Pts were treated with escalating doses of NFV (1250-2500 mg b.i.d) in combination with lenalidomide 25mg daily (d 1 - 21) and dexamethasone 40/20 mg (days 1, 8, 15, 22 every 4 weeks) for up to 4 cycles. In the phase II part a Simon's two stage design was used to investigate an objective response rate (ORR) ≤ 10% versus ORR ≥ 30% (alpha 5%, power 80%) requiring 29 pts. Pharmacodynamic parameters (proteasome activity, activation of the UPR and autophagy) were assessed from PBMC collected at baseline, d 8 and 15 in the phase I part from 7 pts (ClinicalTrials.gov NCT01555281).ResultsIn phase I, 10 pts were analyzed for dose limiting toxicities (DLTs). 2 DLTs were observed: diarrhea grade 3 and thrombocytopenia grade 4 at dose level 1850 mg b.i.d. NFV 1250 mg b.i.d. was identified as the recommended dose for phase II. 29 pts including 6 pts from phase I with advanced, lenalidomide-refractory (IMWG criteria) myeloma were analyzed for phase II. 25 pts (86%) had undergone 2 or more prior lines of therapy, 18 pts (62%) had prior autologous stem cell transplantation, 8 pts (28%) had high risk cytogenetic features. 16 pts (55%) achieved an objective response (MR or better, 95% CI 36-74), VGPR was reached in 3 pts (10%), PR in 6 pts (21%), and MR in 7 pts (24%), SD in 4 pts (14%), PD in 7 pts (24%), 2 pts were not evaluable. Of 8 pts with high risk cytogenetics we observed 1 VGPR and 2 PR. The median duration of response was 4 months (95% CI 1.8-5.7) and median overall survival was 21.6 months (95% CI 13.0-50.1). 14/29 pts discontinued trial treatment due to: unacceptable toxicity (4 pts), progressive disease (8 pts), patient refusal (2 pts). Most frequently observed adverse events were grade 1 gastrointestinal symptoms (9 pts) and metabolic disorders (9 pts). Hematologic adverse events of grade 3 or more were anemia (7 pts), thrombocytopenia (6 pts) and neutropenia (7 pts, including 2 with febrile neutropenia). Non-hematologic adverse events of grade 3 or more occurring in > 1 patient were: dyspnea (3 pts), fatigue (3 pts), lung infection (3 pts) and bone pain (2 pts).We performed quantitative pharmacodynamic monitoring of proteasome activity and of protein expression indicating an activation of the unfolded protein response (IRE1, CHOP) and autophagy (LC3). We observed a mean overall reduction of 45% (95% CI 40-51) of total proteasome activity in PBMC at days 8 or 15 during treatment with nelfinavir/lenalidomide/dexamethasone, compared to baseline.ConclusionThe addition of NFV 1250 mg b.i.d. to Rd therapy is a safe and active oral combination for treatment of relapsed, lenalidomide-refractory myeloma. The proteasome-inhibiting activity of nelfinavir in combination with Rd is noteworthy and may be the basis for the clinical activity. Our data support the continued development of NFV as a myeloma drug. NFV is an oral, cost-effective drug to re-sensitize myeloma patients for lenalidomide therapy. DisclosuresHitz:Celgene: Consultancy. Panagiotis:Celgene, Takeda, Amgen, Novartis, Janssen: Consultancy, Honoraria. Mey:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

The integrated stress response promotes B7H6 expression

The B7 family member, B7H6, is a ligand for the natural killer cell receptor NKp30. B7H6 is hardly expressed on normal tissues, but undergoes upregulation on different types of tumors, implicating it as an attractive target for cancer immunotherapy. The molecular mechanisms that control B7H6 expression are poorly understood. We report that in contrast to other NK cell ligands, endoplasmic reticulum (ER) stress upregulates B7H6 mRNA levels and surface expression. B7H6 induction by ER stress requires protein kinase R-like ER kinase (PERK), one of the three canonical sensors of the unfolded protein response. PERK phosphorylates eIF2α, which regulates protein synthesis and gene expression. Because eIF2α is phosphorylated by several kinases following different stress conditions, the program downstream to eIF2α phosphorylation is called the integrated stress response (ISR). Several drugs were reported to promote the ISR. Nelfinavir and lopinavir, two clinically approved HIV protease inhibitors, promote eIF2α phosphorylation by different mechanisms. We show that nelfinavir and lopinavir sustainably instigate B7H6 expression at their pharmacologically relevant concentrations. As such, ER stress and ISR conditions sensitize melanoma targets to CAR-T cells directed against B7H6. Our study highlights a novel mechanism to induce B7H6 expression and suggests a pharmacological approach to improve B7H6-directed immunotherapy.Key messagesB7H6 is induced by ER stress in a PERK-dependent mechanism.Induction of B7H6 is obtained pharmacologically by HIV protease inhibitors.Exposure of tumor cells to the HIV protease inhibitor nelfinavir improves the recognition by B7H6-directed CAR-T.

High-mobility group box 1 protein is involved in the protective effect of Saquinavir on ventilation-induced lung injury in mice.

Saquinavir (SQV) is the first FDA approved HIV protease inhibitor. Previous studies showed that SQV can limit Toll-like receptor-4 (TLR4)-mediated inflammatory pathway and nuclear factor-κB (NF-κB) activation, thereby playing a protective role in many kinds of diseases. High-mobility group box 1 (HMGB1) has been identified as an inflammatory mediator and it might express its toxicity in a short period of time in ventilator-induced lung injury (VILI). In this study, C57BL/6 mice were randomly divided into four groups (n = 10): control group and control with SQV group (Con + SQV) were spontaneous breath. HTV group (HTV) received high tidal volume ventilation (HTV) for 4 h. HTV with SQV group (HTV + SQV) were pretreated with 5 mg/kg of SQV for 7 days before HTV. Mice were sacrificed after 4 h of HTV. Lung wet/dry weight (W/D) ratio, alveolar-capillary permeability to Evans blue albumin (EBA), cell counts, total proteins in bronchoalveolar lavage fluid (BALF), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) level in BALF and lung tissue, and lung histopathology were examined. Our results showed that HTV caused significant lung injury and NF-κB activation, which was correlated with the increase of TNF-α and IL-6 levels in BALF and plasma. SQV pretreatment significantly attenuated pulmonary inflammatory injury, as well as NF-κB activation. These findings indicate that the protective effect of SQV may be associated with the inhibition of NF-κB activation and HMGB1 expression in mice.

The NO-modified HIV protease inhibitor as a valuable drug for hematological malignancies: Role of p70S6K

Covalent attachment of NO to the first approved HIV protease inhibitor Saquinavir (Saq-NO) expands the therapeutic potential of the original drug. Apart from retained antiviral activity, the modified drug exerts strong antitumor effects and lower toxicity. In the present study, we have evaluated the sensitivity of different hematological malignancies to Saq-NO. Saq-NO efficiently diminished the viability of Jurkat, Raji, HL-60 and K562 cells. While Jurkat and Raji cells (established from pediatric patients) displayed abrogated proliferative potential, HL-60 and K652 cells (originated from adults) exposed to Saq-NO treatment underwent caspase dependent apoptosis. In addition, similar sensitivity to Saq-NO was observed in mononuclear blood cells obtained from pediatric patients with acute lymphoblastic leukemia (ALL) and adult patients with acute myeloid leukemia (AML). Western blot analysis indicated p70S6 kinase as a possible intracellular target of Saq-NO action. Moreover, the addition of a NO moiety to Lopinavir resulted in improved antitumor potential as compared to the parental compound, suggesting that NO-derived HIV protease inhibitors are a potential new source of anticancer drugs with unique mode of action.

Development and characterization of folate anchored Saquinavir entrapped PLGA nanoparticles for anti-tumor activity

Objective: Saquinavir (SQV) is a US-FDA approved HIV protease inhibitor (HPI) for HIV cure. The purpose of the present investigation was to develop and characterize the anticancer potential of the SQV-loaded folic acid (FA) conjugated PEGylated and non-PEGylated poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (NPs) (SQV–Fol–PEG–PLGA and SQV–Fol–PLGA) employing PC-3 (human prostate) and MCF-7 (human breast) cancer cell lines.Materials and methods: Developed NPs were characterized by IR, NMR, DSC, XRD, size, charge and further tested for drug loading and cellular uptake properties.Result: The entrapment efficiency was found to be 56 ± 0.60 and 58 ± 0.80 w/v for SQV–Fol–PEG–PLGA and SQV–PLGA NPs, respectively. The obtained results of SQV–Fol–PEG–PLGA showed enhanced cytotoxicity and cellular uptake and were most preferentially taken up by the cancerous cells via folate receptor-mediated endocytosis (RME) mechanism. At 260 µM concentration, SQV–PLGA NPs and SQV–Fol–PEG–PLGA NPs showed 20%, 20% and 23% cell growth inhibition in PC-3 cells, respectively whereas in MCF-7 cells it was 12%, 15% and 14% cell growth inhibition, respectively.Conclusions: Developed targeted SQV–Fol–PEG–PLGA NPs were superior anticancer potential as compared to non-targeted SQV–PLGA NPs. Thus, these targeted NPs provide another option for anticancer drug delivery scientists.

Ritonavir-Mediated Induction of Apoptosis in Pancreatic Cancer Occurs via the RB/E2F-1 and AKT Pathways

Recent observations suggest a lower incidence of malignancies in patients infected with HIV during treatment with Highly Active Anti-Retroviral Therapy (HAART) utilizing protease inhibitors. We investigated the effects of ritonavir, a FDA approved HIV protease inhibitor, on proliferation of pancreatic ductal adeno-carcinoma (PDAC) cell lines. Human PDAC cell lines BxPC-3, MIA PaCa-2, and PANC-1 were propagated under standard conditions and treated with serial dilutions of ritonavir. Ritonavir inhibited cell growth in a dose-dependent manner as well as activated the intrinsic apoptotic pathway in human pancreatic ductal adenocarcinoma (PDAC) cell lines. We observed down-modulation of cell-cycle promoting and up-regulation of cell-cycle inhibitory genes; enhanced interaction of retinoblastoma protein (RB) with E2F-1 transcription factor; inhibition of phosphorylation of RB, resulting in sequestration of E2F-1 and subsequent down-regulation of S phase genes; decreased interaction of E2F-1 with its consensus binding sites; inhibition of cell motility and invasiveness; and inhibition of the AKT pathway. Our results demonstrate a potential use of ritonavir as part of combination chemotherapy for PDAC. Since ritonavir is FDA approved for HIV, drug repositioning for PDAC would limit the costs and reduce risks.

Molecular Docking Studies and Comparative Binding Mode Analysis of FDA Approved HIV Protease Inhibitors

Molecular Docking Studies and Comparative Binding Mode Analysis of FDA Approved HIV Protease Inhibitors

Stereoselective Synthesis of cis‐Fused Perhydrofuro[2,3‐b]furan Derivatives from Sugar‐Derived Allyl Vinyl Ethers

AbstractA stereoselective methodology has been developed for the construction of cis‐fused perhydrofuro[2,3‐b]furans, via 3‐C‐branched glycal derivatives, involving Claisen rearrangement of sugar‐derived allyl vinyl ethers, followed by a one‐pot ozonolysis and acid‐mediated acetalization. The methodology was used for the stereoselective synthesis of the P2 ligand in the recently FDA approved HIV protease inhibitor darunavir (Prezista). The methodology was also successfully used for the synthesis of cis‐fused perhydro‐5‐oxofuro[2,3‐b]furan derivatives.

Myeloma Exhibits Dependence on Atypical Glucose Transporters: Targeting MCL-1 Through GLUT4 Inhibition

Abstract 1850Multiple Myeloma (MM) is an incurable heterogeneous B cell malignancy characterized by hyperdiploidy and/or aberrant chromosomal translocations warranting strategies that can target diverse molecular subtypes. One such unifying feature in MM entails an increased avidity for glucose that forms the basis for clinical imaging of myeloma by 18fluoro-deoxyglucose positron emission tomography. We are however not yet able to target abnormal glucose utilization for therapy. Given that glucose entry is a key rate-limiting step in glycolysis we performed an unbiased multi-cell line gene-expression profiling study combined with functional knock-down experiments to determine critical glucose transporters facilitating glucose entry in myeloma. These studies revealed a critical dependence of myeloma on the insulin-responsive glucose transporter GLUT4, and GLUTs 8 and 11. Our data demonstrate that myeloma cells exhibit a significant reliance on constitutively cell surface-localized GLUT4 for basal glucose consumption and viability. The functional significance of these transporters was further bolstered by detection of similar patterns of expression in myeloma patient samples. We also tested the therapeutic utility of targeting plasma-membrane localized GLUT4 in MM cell lines and patient samples with the FDA approved HIV protease inhibitor ritonavir that has an off-target inhibitory effect on GLUT4, providing proof of principle that GLUTs can be targeted for therapeutic benefit.In this study we have investigated the mechanism by which GLUT4 suppression elicits cell death in myeloma. GLUT4 contributes to a significant fraction of glucose entry in myeloma while GLUTs 8 and 11 appear to have a significant impact on myeloma cell viability relating to alternative enigmatic subcellular functions not reliant on glucose entry per se. To further elucidate the mechanisms associated with cell death upon glucose deprivation in response to GLUT4 suppression, we examined expression levels of key apoptotic effectors in three myeloma cell lines expressing GLUT 1, 4, 8 or 11 shRNAs. Suppression of GLUT4 appears to selectively engage an apoptotic cascade involving suppression of MCL-1 and BCL-xL in addition to an increase in pro-apoptotic BAX expression. We do not detect up-regulation of PUMA or NOXA that have previously been demonstrated to play a role in glucose-deprivation induced cell death in other cell types. The suppression of MCL-1 is associated with an upstream activation of GSK-3. Expression of an MCL-1 ubiquitination-resistant mutant prevents reduction of MCL-1 protein upon GLUT4 knockdown, and reverses the toxicity elicited by GLUT4 suppression. In addition we do not detect the appearance of the cleaved pro-apoptotic fragment of MCL-1. These observations suggest glucose-deprivation induced cell death in response to GLUT4 reduction is mediated by ubiquitination and proteasomal degradation of MCL-1.In sum we have discovered a novel myeloma specific method to target glucose entry and elicit apoptosis via suppression of MCL-1 expression. MCL-1 is a key effector of chemo-resistance in MM with levels of expression correlating to disease severity. Therefore strategies that can target MCL-1 will have significant utility in treatment of this fatal malignancy. These observations provide further rationale for the development of GLUT4-specific biologics to target aberrant glucose metabolism in myeloma and potentially other glucose-driven cancers. Disclosures:No relevant conflicts of interest to declare.

Abstract 1586: Oral administration of HIV-protease inhibitors reduces ovarian tumor growth in vivo

Abstract INTRODUCTION: Ritonavir boosted lopinavir (LPV/r) is an FDA approved HIV-protease inhibitor combination that is a well tolerated and preferred treatment for HIV patients. Ritonavir is a potent irreversible inhibitor of cytochrome P450 isoform 3A (CYP3A) which can substantially increase bioavailability of lopinavir in vivo. This combination of lopinavir and ritonavir has been shown to increase the efficacy of reducing viral load in AIDS patients. HIV patients taking antiretroviral protease inhibitors such as LPV/r have a lower incidence of HIV associated malignancies such as non-Hodgkin's lymphoma, cervical cancer and Kaposi's sarcoma, leading to the hypothesis that these drugs have antineoplastic activity. Given the need for novel treatment approaches in ovarian cancer, we are investigating the antineoplastic effects of LPV/r, in vivo. METHODS: A xenograph model of ovarian cancer is used to assess the antineoplastic effect of LPV/r in vivo. Oral doses of LPV/r dissolved in corn oil are administered to mice over the course of 2-3 weeks. Tumor area and mouse weight are monitored. After 2-3 weeks tumors are harvested and analyzed. RESULTS: Preliminary results indicate that LPV/r administered orally in combination with a high fat diet inhibits tumor growth in vivo without inducing weight loss. In contrast, the dose of intraperitoneal cisplatin required to attain a similar antineoplastic effect resulted in significant weight loss and morbidity. CONCLUSIONS: Because protease inhibitors can induce both apoptotic and non-apoptotic ovarian cancer cell death in vitro and in vivo, these drugs may circumvent chemoresistance due to alterations in apoptotic response. Our data suggests that LPV/r may also have clinical application in the treatment of ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1586. doi:10.1158/1538-7445.AM2011-1586

A phase I study of nelfinavir, an FDA approved HIV protease inhibitor, in adults with refractory solid tumors

2583 Background: Preclinical studies show that HIV protease inhibitors such as nelfinavir (N) have dose- dependent, pleiotropic anti-cancer activities. However, the maximum tolerated dose (MTD) of N has not been established in humans. Methods: Pts were treated on a modified Fibonacci dose-escalation scheme with a twice daily oral dose of N starting at the FDA approved dose of 1250 mg bid on a 21-day cycle. Patients with refractory solid tumors, ECOG PS < 2, and adequate organ function were eligible. Therapy continued until MTD or disease progression. PBMCs as well as optional tumor biopsies were collected for Akt inhibition and expression of markers of ER stress (ERS). Results: 14 patients have been enrolled. Of the 11 evaluable for toxicity, there were 10 men, 10 Caucasians, and 1 African American (median age 63 years (range 24 - 77)). Tumor types included NSCLC (3), SCLC (2), thyroid (3), pancreatic (1), colorectal (1), and renal cell (1). Median number of prior systemic therapies was 2 (range, 1 - 6). There have been no grade 4 or 5 toxicities. We observed 12 grade 3 toxicities that were asymptomatic laboratory abnormalities. The most prevalent toxicities were ALT transaminitis (5 events in 8 subjects in dose level ((DL) 2, 3, 4), AST transaminitis (4 events in 8 subjects in DL 2, 4), diarrhea (8 events in 5 subjects in DL 2, 3, 4), and hyperglycemia (5 events in 5 subjects in DL 1, 2, 3). Enrollment continues at DL 4 (3125 mg twice daily). There have been no responses. Two subjects with lung cancer had stable disease for 9 weeks. Pharmacokinetic data revealed median Cmax of 2,461.5 ng/ml (DL1), 11,809 ng/ml (DL2), 11,576 ng/ml (DL3), and 11,986 ng/ml (DL4), occurring 4 hours after an oral dose. There was no relationship between the drug levels and albumin levels. Akt inhibition and increased expression of markers of ERS and apoptosis have been observed in PBMCs from week 1 in the majority of patients at every dose level, but there was no correlation with clinical response. Conclusions: N appears to be well tolerated in subjects with advanced solid tumors at 2.5 times the FDA approved dose. AUC data suggest that there may be only minimal increases in plasma drug concentrations with doses above 1875 mg twice daily. No significant financial relationships to disclose.

Inhibition of Autophagy Promotes Bortezomib-Mediated Cell Death in Myeloma Cells

The 26S proteasome is a key regulator of proteins controlling many important cellular functions, including cell cycle progression, differentiation, gene transcription and apoptosis. Proteasome inhibition is a new therapeutic strategy that has shown promise in the treatment of B cell malignancies, primarily multiple myeloma. We and others have demonstrated that proteasome inhibitors induce endoplasmic reticulum (ER) stress and activate an unfolded protein response (UPR) in transformed cells. Our previous work demonstrated that bortezomib induces an endoplasmic reticulum (ER) stress response ultimately leading to calcium-dependent apoptotic cell death. Co-treatment of myeloma cells with the mitochondrial uniporter inhibitor ruthenium red (RuR) abrogated bortezomib mediated cell death, indicating that the cytotoxic effects of proteasomal inhibition requires dysregulation of intracellular Ca2+. Intracellular Ca2+ has also been implicated in the cellular stress response known as autophagy or “self-eating”. Macroautophagy (hereafter referred to as autophagy) is induced by various cellular stresses including nutrient deprivation, metabolic insufficiency, interruption of growth factor signaling, elevated ROS, accumulation of intracellular Ca2+, and the UPR. The biochemical events linking the cellular stress response with the induction of autophagy, and the relationship between autophagy and apoptosis is not well understood.In this study, we investigate the role of the Ca2+ dependent serine protease, calpain, as a mediator of the conversion from autophagic cell survival to accelerated cell death in the ER stress response. We demonstrate that the proteasome inhibitor, bortezomib, initiates autophagy in myeloma cells, and protection from bortezomib-mediated cell death by mitochondrial Ca2+ inhibitors is associated with a promotion and stabilization of the autophagosome. This response can be reversed, and indeed, accelerated, leading to enhanced cell death, by blockade of calpain activity. Inhibition of calpain activity with the tri-peptide zLLY-FMK (Calpain Inhibitor IV, (CiIV) or the non-peptide inhibitor, PD150606, demonstrated a significant increase in the cytotoxic activity of bortezomib. Similarly, elimination of the small catalytic subunit, CAPNS1, using siRNA, enhanced bortezomib-mediated cell death, and prevented autophagosome-lysosomal progression. Furthermore, inhibition of calpain by clinically approved HIV protease inhibitors including Nelfinavir, Ritonavir, Saquinavir, and Indinavir sulfate, significantly increased the cytotoxic activity of bortezomib in vitro. We suggest that disregulation of Ca2+ by bortezomib-mediated ER stress activates the autophagic survival response. Inhibition of mitochondrial Ca2+ uptake by the uniporter inhibitor RuR promotes autophagy, and confers resistance to bortezomib. Conversely, inhibition of the Ca2+-dependent serine protease, calpain, prevents autophagolysosome maturation, and subverts the survival response to cell death. These data are likely to have important clinical implications for the treatment of refractory myeloma and other B cell malignancies.

Fast and simultaneous determination of darunavir and eleven other antiretroviral drugs for therapeutic drug monitoring: method development and validation for the determination of all currently approved HIV protease inhibitors and non‐nucleoside reverse transcriptase inhibitors in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

For the quantification of all currently approved non-nucleoside reverse transcriptase inhibitors and protease inhibitors, including the new protease inhibitor darunavir and the active nelfinavir metabolite M8, an assay was developed, using liquid chromatography coupled with tandem mass spectrometry. The sample pretreatment consisted of a protein precipitation with a mixture of methanol and acetonitrile using only 100 microL plasma. Chromatographic separation was performed on a reversed-phase C18 column (150 x 2.0 mm, particle size 5 microm) with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.25 mL/min. The analytical run time was only 10 min. The triple quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over a range of 0.1 to 20 microg/mL for amprenavir, atazanavir, efavirenz, indinavir, lopinavir, nelfinavir, the active nelfinavir metabolite M8, nevirapine and ritonavir, a range of 0.05 to 10 microg/mL for saquinavir and darunavir and a range of 0.5 to 100 microg/mL for tipranavir, based on observed concentration ranges in patients treated with these drugs. D5-squinavir, D6-indinavir, 13C6-efavirenz and dibenzepine were used as internal standards. The method was proven to be specific, accurate, precise and robust. Accuracies ranged from 88.5% to 102.2% and all precisions were less than 9.5%. Furthermore, the assay demonstrates a high sensitivity for all analytes and the stepwise gradient allows addition of new analytes into the same method. The method is now successfully applied for routine therapeutic drug monitoring and pharmacokinetic studies in HIV-infected patients.

Drug Interactions of Tipranavir, a New HIV Protease Inhibitor

Tipranavir is one of the latest approved HIV protease inhibitors. This non-peptidic molecule is an strong inducer of cytochrome P450 and has to be co-administered with low doses ritonavir as pharmacokinetic booster to achieve effective antiviral activity in vivo. As expected, significant drug interactions may occur in patients treated with tipranavir/ritonavir, including diminished exposure to some antiretroviral agents. Although a few interactions can be managed with adequate drug dosing others preclude to use these medications in combination.

Atazanavir trough plasma concentration monitoring in a cohort of HIV-1-positive individuals receiving highly active antiretroviral therapy

Atazanavir is a recently approved HIV protease inhibitor (PI). As with other PIs, careful attention to potential pharmacokinetic drug interactions in clinical practice is necessary. The aim of this study was to assess the clinical associations with plasma atazanavir concentrations in HIV-positive individuals. Individuals established on an atazanavir-containing regimen, completed an interviewer-administered questionnaire recording atazanavir dosing characteristics, concomitant medication use and adherence. After completion, plasma atazanavir concentrations were measured. Of 100 individuals, mean trough plasma atazanavir concentrations (mug/L) were 282 (95% CI 95-468, n = 19) and 774 (95% CI 646-902, n = 81) in those on non- and ritonavir-boosted atazanavir regimens, respectively. Eighty-five individuals had HIV RNA <50 copies/mL. Seven individuals had atazanavir plasma concentrations below the assay limit of detection (<50 microg/L), all of whom had undetectable plasma HIV RNA. In a multivariate analysis, nevirapine use was associated with significantly lower trough atazanavir concentrations (P = 0.011) and lopinavir/ritonavir use with higher trough atazanavir concentrations (P = 0.032). Dosing characteristics (including food taken), concomitant medications (including drugs used for dyspepsia) and HIV RNA were not significantly associated with trough atazanavir concentrations. In this cohort, despite the wide inter-individual variability of atazanavir trough concentrations, no significant association with dosing characteristics, concomitant medication (with the exception of nevirapine and lopinavir/ritonavir) or virological response was observed. Further work is needed to assess the optimal dosing regimen when using atazanavir with nevirapine.

Predictors of Virological Response to Atazanavir in Protease Inhibitor-Experienced Patients

Background: Atazanavir (ATV) is the latest approved HIV protease inhibitor (PI). Even though it is very convenient (only two capsules once a day), concerns have risen about its potency. Method: The clinical performance of ATV 400 mg once a day was examined in all PI-experienced patients who were included in the ATV expanded access program conducted in a single institution. The predictive value of baseline drug resistance HIV genotypes, ATV plasma trough levels, and the genotypic inhibitory quotient (GIQ) on the virological response at week 24 was assessed. Results: Data from 92 patients were analyzed. ATV was prescribed as part of a rescue intervention (45%), a simplification strategy (11%), or an attempt to ameliorate hyperlipidemias (23%) or other toxicities (16%). Tenofovir (TDF) was concomitantly used with ATV in 78% of patients. None received ritonavir boosting. In patients with detectable viremia at baseline (65%), the median HIV RNA drop was 0.7 logs. The median ATV Cmin was 0.12 μg/mL (IQR, 0.05-0.22 μg/mL), which is clearly above the IC90 (90% inhibitory concentration) for ATV in wild-type viruses. The virological response did not correlate significantly with ATV Cmin. The median number of protease resistance mutations was lower in patients showing virological response than in nonresponders (1 vs. 5; p = .07). A higher HIV RNA drop was associated with a higher GIQ (p = .02; β = –5.4; 95% CI, –10 to –1). Only 4 patients (4%) discontinued treatment due to ATV-related toxicities (hyperbilirubinemia in 1). Bilirubin levels were associated with ATV plasma concentrations (p = .05; β = 3.2; 95% CI, –0.1 to 6.5). The rate of hypertriglyceridemia and hypercholesterolemia declined significantly with respect to baseline. Conclusion: ATV is relatively safe and provides significant virological response in PI-experienced patients, mainly among those with a low number of protease resistance mutations. The GIQ predicts accurately the virological response in patients receiving ATV. Hyperbilirubinemia is associated with higher ATV plasma levels.

Non-peptidic HIV protease inhibitors.

The past decade has seen many exciting achievements and advances in the treatment of HIV infection. One of the key components in this ever-evolving remedial strategy has been medicinally efficacious enzymatic inhibitors targeting the essential viral aspartyl protease. While the use of currently approved HIV protease inhibitors in concert with drugs that target the reverse transcriptase has dramatically ameliorated the disease state for many individuals, highly-structured dosing regimens accompanied by adverse side-effect profiles have led to a significant level of patient non-compliance. In addition, the development of and selection for resistant mutants have limited the long-term therapeutic outlook of the current protease inhibitors. The need for complementary agents in this salutary class addressing these challenges and opportunities is vividly clear. To this end, much attention and focus has been placed on cyclic, non-peptidic protease inhibitors, exemplified by dihydropyrones and ureas, and their possible future role in this medicinal campaign. The strategies to their design as well as their biological, pharmacokinetic and resistance profiles, and their clinical application will be discussed.

Peptidomimetic inhibitors of HIV protease.

There are currently (July, 2002) six protease inhibitors approved for the treatment of HIV infection, each of which can be classified as peptidomimetic in structure. These agents, when used in combination with other antiretroviral agents, produce a sustained decrease in viral load, often to levels below the limits of quantifiable detection, and a significant reconstitution of the immune system. Therapeutic regimens containing one or more HIV protease inhibitors thus provide a highly effective method for disease management. The important role of protease inhibitors in HIV therapy, combined with numerous challenges remaining in HIV treatment, have resulted in a continued effort both to optimize regimens using the existing agents and to identify new protease inhibitors that may provide unique properties. This review will provide an overview of the discovery and clinical trials of the currently approved HIV protease inhibitors, followed by an examination of important aspects of therapy, such as pharmacokinetic enhancement, resistance and side effects. A description of new peptidomimetic compounds currently being investigated in the clinic and in preclinical discovery will follow.

Syntheses of FDA Approved HIV Protease Inhibitors.

The treatment of HIV and AIDS was revolutionized by the introduction of peptidomimetic aspartyl protease inhibitors. One of the major limitations of this type of therapy is that higher therapeutic doses are necessary because of the presence of 'peptide-like' features in the drugs. Therefore, adequate supplies and cost effective syntheses of these drugs are of utmost importance. To date, there are six protease inhibitors approved by the United States Food and Drug Administration (FDA) for the treatment of HIV and AIDS. This review focuses on the published syntheses of currently FDA approved HIV protease inhibitor drugs, their isosteres and ligands.