HIV/AIDS: the management of treatment-experienced HIV-infected patients: new drugs and drug combinations

A foundation for reference models for drug combinations with an application to Loewe's reference model

Background

Treating patients with combinations of drugs that have synergistic effects has become widespread practice in the clinic. Drugs work synergistically when the observed effect of a drug combination is larger than the effect predicted by the reference model. The reference model is a theoretical null model that returns the combined effect of given doses of drugs under the assumption that these drugs do not interact. There is ongoing debate on what it means for drugs to not interact. The controversy transcends mathematical punctuality, as different non-interaction principles result in different reference models. A famous reference model that has been in existence for already a long time is Loewe’s reference model. Loewe’s vision on non-interaction was purely intuitive: two drugs do not interact if all combinations of doses that result in a certain given effect lie on a straight line.

Results

We show that Loewe’s reference model can be obtained from much more fundamental principles. First, we introduce the new notion of complementary dose. Secondly, we reformulate the existing concept of equivalent dose, whereby our formulation is more general than existing ones. Finally, a very general non-interaction principle is put forward. The proposed non-interaction principle represents a certain interplay between complementary and equivalent doses: drugs are non-interacting if complementarity is preserved under equivalence. It is then shown that Loewe’s reference model naturally follows from these principles by an appropriate choice of complementarity.

Conclusions

The presented work increases insight into Loewe’s reference model for drug combinations, which is realized by the introduction of a very general non-interaction principle that does not refer to any specific dose-response curve, nor to any property of applicable dose-response curves.

Long-term virological effectiveness with darunavir/ritonavir-based salvage therapy in people living with HIV/AIDS from São Paulo, Brazil

Even though darunavir/ritonavir (DRV/r) has high potency and a greater genetic barrier, there are few studies on the long-term effectiveness of DRV/r-based salvage therapy in people living with HIV (PLWH) in low and middle-income countries. This retrospective cohort study, from São Paulo, Brazil, included ART-experienced PLWH aged ≥18 years with virological failure (VF) who had started DRV/r plus an optimized background regimen (OBR) between 2008 and 2012. The proportion of patients with viral load (VL) <50 copies/mL, the improved mean CD4+ T cell count and the factors associated with VF during the 144-week follow-up were assessed. The study included 173 patients with the following characteristics [median (interquartile range)]: age 48 (42 -53) years; CD4+ T cell count, 229 (89 -376) cells/mm3; VL, 4.26 (3.70 -4.74) log10; 6 (4 -7) previous regimens; and 100 (38 -156) months of VF. After 144 weeks, 129 (75%) patients had VL< 50 copies/mL and a mean increase in the CD4+ T cell count of 190 cells/mm3. VL>100,000 copies/mL and poor adherence were associated with VF. DRV/r plus an OBR showed high long-term virological suppression and immunological recovery. VL>100,000 copies/mL and poor adherence were associated with VF at 144 weeks.

Management of Advanced HIV Disease

Great progress has been made in caring for persons with human immunodeficiency virus. However, a significant proportion of individuals still present to care with advanced disease and a low CD4 count. Careful considerations for selection of antiretroviral therapy as well as close monitoring for opportunistic infections and immune reconstitution inflammatory syndrome are vitally important in providing care for such individuals.

Virologic Effectiveness of Abacavir/Lamivudine with Darunavir/Ritonavir Versus Other Protease Inhibitors in Treatment-Experienced HIV-Infected Patients in Clinical Practice

Background and Objectives

The standard of care for HIV treatment is a three-drug regimen consisting of two nucleoside reverse transcriptase inhibitors (NRTIs) and either a non-nucleoside reverse transcriptase inhibitor, a protease inhibitor (PI) or an integrase strand transfer inhibitor. Darunavir boosted with ritonavir (DRV/r) is the only preferred PI in the US Department of Health and Human Services (DHHS) HIV treatment guidelines for antiretroviral-naïve patients, recommended in combination with tenofovir/emtricitabine for antiretroviral-naïve patients. For treatment-experienced and certain antiretroviral-naïve patients, abacavir and lamivudine (ABC/3TC) in combination with DRV/r is considered an effective and tolerable alternative, despite limited research on the effectiveness of this particular combination. This study evaluated virologic outcomes in treatment-experienced patients taking ABC/3TC + DRV/r compared to treatment-experienced patients taking ABC/3TC with any other PI.

Methods

Treatment-experienced HIV-infected patients initiating their first regimen containing ABC/3TC in combination with any PI in the year 2005 or later were selected from the Observational Pharmaco-Epidemiology Research and Analysis (OPERA^®) cohort, a prospective observational cohort reflecting routine medical care. Viral load measurements taken during follow-up were compared between patients taking ABC/3TC + DRV/r and ABC/3TC with a PI other than DRV/r. Logistic regression models were fit to assess the association between regimen exposure and viral load suppression.

Results

A total of 151 patients initiating ABC/3TC + DRV/r and 525 patients initiating ABC/3TC + a non-darunavir PI were included. Patients in both treatment groups had comparable clinical indicators (viral load, CD4) at baseline. A regimen of ABC/3TC + DRV/r was more likely to be prescribed in the later years of the study period, leading to a shorter median follow-up in the DRV/r treatment group (as-treated analysis: 14 vs. 17 months, p = 0.04; intent-to-treat analysis: 33 vs. 68 months, p < 0.001). Multivariable logistic regression models accounting for year of regimen initiation, among other factors, indicated no statistically significant differences in achieving an undetectable viral load for patients taking DRV/r with ABC/3TC compared with other PIs, both in the as-treated (odds ratio [95 % confidence interval]: 0.84 [0.53–1.34]) and intent-to-treat analyses (0.82 [0.48–1.40]). Patients in both treatment groups also showed similar reductions in viral load (median darunavir vs. non-darunavir: −23.0 vs. −23.0 copies/mL; p = 0.72) and gains in CD4 T cell counts (median darunavir vs. non-darunavir: 106 vs. 108 cells/mm³; p = 0.59] while being treated with the regimen of interest.

Conclusions

Patients receiving ABC/3TC + DRV/r appear to experience similar treatment benefit to patients taking ABC/3TC with other PIs in terms of achieving suppression, as well as absolute reductions in viral load and CD4 lymphocyte gains.

Effectiveness and risk factors for virological outcome of darunavir-based therapy for treatment-experienced HIV-infected patients

OBJECTIVE

We evaluated the effectiveness of darunavir (DRV) treatment plus an optimized background regimen in 120 HIV-1 treatment-experienced patients.

DESIGN

Retrospective cohort, multicenter study.

METHODS

Adults >16 years with virological treatment failure starting therapy with a DRV-containing regimen were included. Effectiveness was evaluated as the percentage of patients with an undetectable HIV-1 RNA viral load (<50 and <200 copies/mL) after 48 weeks, and changes in CD4+ cell counts. We evaluated the risk factors associated with treatment failure.

RESULTS

Of the cohort, 83 % were men with a median age of 45 years (interquartile range, IQR 40-51). They had experienced treatment for a median of 13 years (IQR 9-17) with a median of six previous regimens (IQR 4-7), all using protease inhibitors. After treatment, 82 % (95 % confidence interval, CI 74-88 %) of patients had an HIV-1 RNA viral load <200 copies/mL and 69 % (95 % CI 60-76 %) had <50 copies/mL. The CD4+ cell count increased by 378 cells/μL (IQR 252-559; P < 0.001 vs. baseline). Risk factors associated with poor outcome were age >40 years [odds ratio, OR 0.15 (95 % CI 0.10-0.78); P = 0.015], use of raltegravir in the regimen [OR 0.37 (95 % CI 0.10-0.97); P = 0.046], and baseline CD4+ cell count <200 cells/μL [OR 2.79 (95 % CI 1.11-6.97); P = 0.028].

CONCLUSION

In this Mexican cohort Darunavir was metabolically safe, well tolerated and achieved high rates of virological suppression in highly treatment-experienced patients infected with HIV-1.

Peptide-derivatized SB105-A10 dendrimer inhibits the infectivity of R5 and X4 HIV-1 strains in primary PBMCs and cervicovaginal histocultures

Peptide dendrimers are a class of molecules that exhibit a large array of biological effects including antiviral activity. In this report, we analyzed the antiviral activity of the peptide-derivatized SB105-A10 dendrimer, which is a tetra-branched dendrimer synthetized on a lysine core, in activated peripheral blood mononuclear cells (PBMCs) that were challenged with reference and wild-type human immunodeficiency virus type 1 (HIV-1) strains. SB105-A10 inhibited infections by HIV-1 X4 and R5 strains, interfering with the early phases of the viral replication cycle. SB105-A10 targets heparan sulfate proteoglycans (HSPGs) and, importantly, the surface plasmon resonance (SPR) assay revealed that SB105-A10 strongly binds gp41 and gp120, most likely preventing HIV-1 attachment/entry through multiple mechanisms. Interestingly, the antiviral activity of SB105-A10 was also detectable in an organ-like structure of human cervicovaginal tissue, in which SB105-A10 inhibited the HIV-1ada R5 strain infection without altering the tissue viability. These results demonstrated the strong antiviral activity of SB105-A10 and suggest a potential microbicide use of this dendrimer to prevent the heterosexual transmission of HIV-1.

Clinical evaluation of Rega 8: an updated genotypic interpretation system that significantly predicts HIV-therapy response

Introduction

Clinically evaluating genotypic interpretation systems is essential to provide optimal guidance in designing potent individualized HIV-regimens. This study aimed at investigating the ability of the latest Rega algorithm to predict virological response on a short and longer period.

Materials & Methods

9231 treatment changes episodes were extracted from an integrated patient database. The virological response after 8, 24 and 48 weeks was dichotomized to success and failure. Success was defined as a viral load below 50 copies/ml or alternatively, a 2 log decrease from the baseline viral load at 8 weeks. The predictive ability of Rega version 8 was analysed in comparison with that of previous evaluated version Rega 5 and two other algorithms (ANRS v2011.05 and Stanford HIVdb v6.0.11). A logistic model based on the genotypic susceptibility score was used to predict virological response, and additionally, confounding factors were added to the model. Performance of the models was compared using the area under the ROC curve (AUC) and a Wilcoxon signed-rank test.

Results

Per unit increase of the GSS reported by Rega 8, the odds on having a successful therapy response on week 8 increased significantly by 81% (OR = 1.81, CI = [1.76–1.86]), on week 24 by 73% (OR = 1.73, CI = [1.69–1.78]) and on week 48 by 85% (OR = 1.85, CI = [1.80–1.91]). No significant differences in AUC were found between the performance of Rega 8 and Rega 5, ANRS v2011.05 and Stanford HIVdb v6.0.11, however Rega 8 had the highest sensitivity: 76.9%, 76.5% and 77.2% on 8, 24 and 48 weeks respectively. Inclusion of additional factors increased the performance significantly.

Conclusion

Rega 8 is a significant predictor for virological response with a better sensitivity than previously, and with rules for recently approved drugs. Additional variables should be taken into account to ensure an effective regimen.

How bioinformatics influences health informatics: usage of biomolecular sequences, expression profiles and automated microscopic image analyses for clinical needs and public health

ABSTRACT

The currently hyped expectation of personalized medicine is often associated with just achieving the information technology led integration of biomolecular sequencing, expression and histopathological bioimaging data with clinical records at the individual patients' level as if the significant biomedical conclusions would be its more or less mandatory result. It remains a sad fact that many, if not most biomolecular mechanisms that translate the human genomic information into phenotypes are not known and, thus, most of the molecular and cellular data cannot be interpreted in terms of biomedically relevant conclusions. Whereas the historical trend will certainly be into the general direction of personalized diagnostics and cures, the temperate view suggests that biomedical applications that rely either on the comparison of biomolecular sequences and/or on the already known biomolecular mechanisms have much greater chances to enter clinical practice soon. In addition to considering the general trends, we exemplarily review advances in the area of cancer biomarker discovery, in the clinically relevant characterization of patient-specific viral and bacterial pathogens (with emphasis on drug selection for influenza and enterohemorrhagic E. coli) as well as progress in the automated assessment of histopathological images. As molecular and cellular data analysis will become instrumental for achieving desirable clinical outcomes, the role of bioinformatics and computational biology approaches will dramatically grow.

AUTHOR SUMMARY

With DNA sequencing and computers becoming increasingly cheap and accessible to the layman, the idea of integrating biomolecular and clinical patient data seems to become a realistic, short-term option that will lead to patient-specific diagnostics and treatment design for many diseases such as cancer, metabolic disorders, inherited conditions, etc. These hyped expectations will fail since many, if not most biomolecular mechanisms that translate the human genomic information into phenotypes are not known yet and, thus, most of the molecular and cellular data collected will not lead to biomedically relevant conclusions. At the same time, less spectacular biomedical applications based on biomolecular sequence comparison and/or known biomolecular mechanisms have the potential to unfold enormous potential for healthcare and public health. Since the analysis of heterogeneous biomolecular data in context with clinical data will be increasingly critical, the role of bioinformatics and computational biology will grow correspondingly in this process.

High rate of virologic suppression with darunavir/ritonavir plus optimized background therapy among highly antiretroviral-experienced HIV-infected patients: results of a prospective cohort study in São Paulo, Brazil

Objectives

To assess the virologic and immunological response of darunavir/ritonavir plus optimized background therapy in highly antiretroviral-experienced HIV-infected patients in Brazil.

Methods

Prospective cohort study carried out in a tertiary center in Sao Paulo, Brazil. Three-class antiretroviral-experienced patients with confirmed virologic failure began darunavir/ritonavir plus optimized background therapy (nucleoside/tide reverse transcriptase inhibitors ± raltegravir ± enfuvirtide ± maraviroc) after performing a genotypic resistance assay. Clinical evaluation and laboratory tests were collected at baseline and at weeks 12, 24, and 48. Multivariate analysis was performed to identify predictors of virologic response at 48 weeks.

Results

Ninety-two patients were included. The median of darunavir resistant mutation was 1 (range 0-6). The median genotypic sensitivity score in the optimized background therapy was 2 (interquartile range 1-2). At week 48, 83% (95% CI: 75–90%) had an HIV RNA level <50 copies/mL and the median CD4 cell count was 301 (interquartile range 224-445) cells/mm³. Baseline HIV RNA >100 000 copies/mL was inversely associated with virologic success at week 48 (HR: 0.22, 95% CI: 0.06-0.85, p = 0.028).

Conclusions

Darunavir/ritonavir plus optimized background therapy was a highly effective salvage regimen under clinical routine conditions in a referral center in Brazil, which is similar to the reported in high-income countries.

The demise of multidrug-resistant HIV-1: the national time trend in Portugal

Objectives

Despite a decreasing mortality and morbidity in treated HIV-1 patients, highly active antiretroviral treatment (HAART) can still fail due to the development of drug resistance. Especially, multidrug-resistant viruses pose a threat to efficient therapy. We studied the changing prevalence of multidrug resistance (MDR) over time in a cohort of HIV-1-infected patients in Portugal.

Patients and methods

We used data of 8065 HIV-1-infected patients followed from July 2001 up to April 2012 in 22 hospitals located in Portugal. MDR at a specific date of sampling was defined as no more than one fully active drug (excluding integrase and entry inhibitors) at that time authorized by the Portuguese National Authority of Medicines and Health Products (INFARMED), as interpreted with the Rega algorithm version 8.0.2. A generalized linear mixed model was used to study the time trend of the prevalence of MDR.

Results

We observed a statistically significant decrease in the prevalence of MDR over the last decade, from 6.9% (95% CI: 5.7–8.4) in 2001–03, 6.0% (95% CI: 4.9–7.2) in 2003–05, 3.7% (95% CI: 2.8–4.8) in 2005–07 and 1.6% (95% CI: 1.1–2.2) in 2007–09 down to 0.6% (95% CI: 0.3–0.9) in 2009–12 [OR = 0.80 (95% CI: 0.75–0.86); P < 0.001]. In July 2011 the last new case of MDR was seen.

Conclusions

The prevalence of multidrug-resistant HIV-1 is decreasing over time in Portugal, reflecting the increasing efficiency of HAART and the availability of new drugs. Therefore, in designing a new drug, safety and practical aspects, e.g. less toxicity and ease of use, may need more attention than focusing mainly on efficacy against resistant strains.

TMC310911, a novel human immunodeficiency virus type 1 protease inhibitor, shows in vitro an improved resistance profile and higher genetic barrier to resistance compared with current protease inhibitors

TMC310911 is a novel human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI) structurally closely related to darunavir (DRV) but with improved virological characteristics. TMC310911 has potent activity against wild-type (WT) HIV-1 (median 50% effective concentration [EC(50)], 14 nM) and a wide spectrum of recombinant HIV-1 clinical isolates, including multiple-PI-resistant strains with decreased susceptibility to currently approved PIs (fold change [FC] in EC(50), >10). For a panel of 2,011 recombinant clinical isolates with decreased susceptibility to at least one of the currently approved PIs, the FC in TMC310911 EC(50) was ≤ 4 for 82% of isolates and ≤ 10 for 96% of isolates. The FC in TMC310911 EC(50) was ≤ 4 and ≤ 10 for 72% and 94% of isolates with decreased susceptibility to DRV, respectively. In vitro resistance selection (IVRS) experiments with WT virus and TMC310911 selected for mutations R41G or R41E, but selection of resistant virus required a longer time than IVRS performed with WT virus and DRV. IVRS performed with r13025, a multiple-PI-resistant recombinant clinical isolate, and TMC310911 selected for mutations L10F, I47V, and L90M (FC in TMC310911 EC(50) = 16). IVRS performed with r13025 in the presence of DRV required less time and resulted in more PI resistance-associated mutations (V32I, I50V, G73S, L76V, and V82I; FC in DRV EC(50) = 258). The activity against a comprehensive panel of PI-resistant mutants and the limited in vitro selection of resistant viruses under drug pressure suggest that TMC310911 represents a potential drug candidate for the management of HIV-1 infection for a broad range of patients, including those with multiple PI resistance.

Pharmacoeconomics of darunavir

Darunavir boosted with ritonavir (DRV/r) in combination with other antiretrovirals (ARVs) was initially approved in 2006 for the treatment of HIV infection in ARV treatment-experienced adults and has subsequently been approved for use in treatment-naive adults in 2008. Clinical studies have shown that DRV/r in combination with other ARVs achieves superior levels of undetectable plasma HIV RNA and generates significant CD4 increases, which reduce the risk of HIV disease progression. Economic evaluations, based on data from controlled clinical trials, found DRV/r combination therapy to generate savings in hospital costs and other non-ARV costs of care in treatment-experienced patients, to maximize the number of patients reaching undetectable plasma HIV RNA, to improve health-related quality of life and quality-adjusted life expectancy, and to be cost effective across different patient populations.

Prevalence, mutation patterns, and effects on protease inhibitor susceptibility of the L76V mutation in HIV-1 protease

Patterns of HIV-1 protease inhibitor (PI) resistance-associated mutations (RAMs) and effects on PI susceptibility associated with the L76V mutation were studied in a large database. Of 20,501 sequences with ≥1 PI RAM, 3.2% contained L76V; L76V was alone in 0.04%. Common partner mutations included M46I, I54V, V82A, I84V, and L90M. L76V was associated with a 2- to 6-fold decrease in susceptibility to lopinavir, darunavir, amprenavir, and indinavir and a 7- to 8-fold increase in susceptibility to atazanavir and saquinavir.

Assessment of the pharmacokinetics of co-administered maraviroc and raltegravir

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Maraviroc is a CCR5 receptor antagonist, while raltegravir is a HIV-1 integrase inhibitor. * Based on the known metabolic pathways (CYP3A4 for maraviroc and UGT1A1 for raltegravir), interaction between the two drugs is unlikely. However, unexpected interactions have been reported for other antiretroviral drugs. * As both these drugs are likely to be used in combination, this study evaluated the pharmacokinetic interaction between them.

WHAT THIS STUDY ADDS

* Relative to individual monotherapy, co-administration resulted in a 20% and 33% decrease in mean C(max), and 14% and 37% decrease in mean AUC of maraviroc and raltegravir, respectively. * Co-administration was generally safe and well tolerated in healthy subjects. * These changes are not likely to be clinically relevant, thus no dose adjustment is necessary.

AIMS

To assess the two-way pharmacokinetic interaction between maraviroc and raltegravir.

METHODS

In this open-label, multiple-dose, fixed-sequence study, 18 healthy, human immunodeficiency virus (HIV)-seronegative subjects received the following: days 1-3 raltegravir 400 mg q12h, days 4-5 washout, days 6-11 maraviroc 300 mg q12h, and days 12-14 raltegravir 400 mg q12h + maraviroc 300 mg q12h. Serial 12-h blood samples were collected on days 3 (raltegravir), 11 (maraviroc) and 14 (raltegravir + maraviroc). Plasma samples were assayed by validated liquid chromatography tandem mass spectrometry assays. Test/reference ratios and 95% confidence intervals (CIs) were determined for pharmacokinetic parameters.

RESULTS

For maraviroc, the test/reference % ratio (95% CI) for AUC(tau) was 85.8 (78.7, 93.5), for C(max) was 79.5 (64.8, 97.5) and for C(min) was 90.3 (84.2, 96.9). For raltegravir, the test/reference % ratio (95% CI) for AUC(tau) was 63.3 (41.0, 97.6), for C(max) was 66.8 (37.1, 120.0) and for C(min) was 72.4 (55.1, 95.2). In all subjects, maraviroc average concentrations (AUC(tau) divided by 12) were >100 ng ml(-1), the threshold value below which there is an increased risk of virological failure. Based on clinical experience for raltegravir, mean C(min) decreases >60% are considered to be clinically relevant for short-term activity; however, in the present study mean changes were only 28% and thus not considered to be of clinical relevance.

CONCLUSIONS

Co-administration of maraviroc and raltegravir decreased systemic exposure of both drugs; however, these are not likely to be clinically relevant. Safety and efficacy studies may help in understanding the role of this combination in the treatment of HIV infection.

Antiretroviral activity of the aminothiol WR1065 against Human Immunodeficiency virus (HIV-1) in vitro and Simian Immunodeficiency virus (SIV) ex vivo

Background

WR1065 is the free-thiol metabolite of the cytoprotective aminothiol amifostine, which is used clinically at very high doses to protect patients against toxicity induced by radiation and chemotherapy. In an earlier study we briefly reported that the aminothiol WR1065 also inhibits HIV-1 replication in phytohemagglutinin (PHA)-stimulated human T-cell blasts (TCBs) infected in culture for 2 hr before WR1065 exposure. In this study we expanded the original observations to define the dose-response curve for that inhibition, and address the question of additive effects for the combination of WR1065 plus Zidovudine (AZT). Here we also explored the effect of WR1065 on SIV by examining TCBs taken from macaques with well-established infections several months with SIV.

Results

TCBs from healthy human donors were infected for 2 hr with HIV-1, and viral replication (p24) was measured after 72 hr of incubation with or without WR1065, AZT, or both drugs. HIV-1 replication, in HIV-1-infected human TCBs, was inhibited by 50% at 13 μM WR1065, a dose at which 80% of the cells were viable. Cell cycle parameters were the same or equivalent at 0, 9.5 and 18.7 μM WR1065, showing no drug-related toxicity. Combination of AZT with WR1065 showed that AZT retained antiretroviral potency in the presence of WR1065. Cultured CD8⁺ T cell-depleted PHA-stimulated TCBs from Macaca mulatta monkeys chronically infected with SIV were incubated 17 days with WR1065, and viral replication (p27) and cell viability were determined. Complete inhibition (100%) of SIV replication (p27) was observed when TCBs from 3 monkeys were incubated for 17 days with 18.7 μM WR1065. A lower dose, 9.5 μM WR1065, completely inhibited SIV replication in 2 of the 3 monkeys, but cells from the third macaque, with the highest viral titer, only responded at the high WR1065 dose.

Conclusion

The study demonstrates that WR1065 and the parent drug amifostine, the FDA-approved drug Ethyol, have antiretroviral activity. WR1065 was active against both an acute infection of HIV-1 and a chronic infection of SIV. The data suggest that the non-toxic drug amifostine may be a useful antiretroviral agent given either alone or in combination with other drugs as adjuvant therapy.

In search of second-generation HIV integrase inhibitors: targeting integration beyond strand transfer

Highly active antiretroviral therapy combines antiviral drugs targeting different steps in the HIV replication cycle in order to reduce viral loads in patients to undetectable levels. Since HIV readily develops resistance and can therefore escape the action of existing drugs, novel drugs with novel mechanisms of action must be developed. The integration of the viral genome into the human genome is an essential and critical replication step that is catalyzed by the viral integrase with the help of cellular cofactors. Although HIV-1 integrase has been studied for more than two decades, the first integrase inhibitor, raltegravir, was only recently approved for clinical use. A second compound, elvitegravir, is currently in advanced clinical trials. Both drugs interfere with the strand-transfer reaction of integrase. Due to the complexity and multistep nature of the integration reaction, several other functions of integrase can be exploited for drug discovery. In this review, we will describe these alternative strategies to inhibit integration. They have recently attracted considerable interest for the development of second-generation integrase inhibitors.

Current peptide HIV type-1 fusion inhibitors

There are now 26 antiretroviral drugs and 6 fixed-dose combinations, including reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors and fusion (or entry) inhibitors, approved by the US Food and Drug Administration for clinical use. Although they are clinically effective when used in combination, none of the existing drugs are considered ideal because of toxic side effects and the ascendance of inducing drug-resistant mutants. Development of new antiviral agents is essential. In the past decades, there has been great progress in understanding the structure of HIV type-1 (HIV-1) gp41 and the mechanism of HIV-1 entry into host cells. This opened up a promising avenue for rationally designed agents to interfere with this process. A number of fusion inhibitors have been developed to block HIV-1 replication. Enfuvirtide (T20) was one of those approved for clinical use. This signalled a new era in AIDS therapeutics. It is a synthetic polypeptide with potent inhibitory activity against HIV-1 infection. However, it is sensitive to proteolytic digestion and resistant virus strains are easily induced with multiple clinical use. One of the directions in designing new fusion inhibitors is to overcome these shortages. In the past years, large numbers of promising fusion inhibitory peptides have emerged. The antiviral activities are more potent or they can act differently from that of T20. Some of these new compounds have great potential to be further developed as therapeutic agents. This article reviewed some recent developments of these peptides and the possible role in anti-HIV-1 therapy.