| Pharmacotherapeutic group: protease inhibitor, ATC code: J05AE09 Mechanism of action The human immunodeficiency virus (HIV-1) encodes an aspartyl protease that is essential for the cleavage and maturation of viral protein precursors. Tipranavir is a non-peptidic inhibitor of the HIV-1 protease that inhibits viral replication by preventing the maturation of viral particles.Antiviral activity in vitroTipranavir inhibits the replication of laboratory strains of HIV-1 and clinical isolates in acute models of T-cell infection, with 50% and 90% effective concentrations (EC50 and EC90) ranging from 0.03 to 0.07 µM (18-42 ng/ml) and 0.07 to 0.18 µM (42-108 ng/ml), respectively. Tipranavir demonstrates antiviral activity in vitro against a broad panel of HIV-1 group M non-clade B isolates (A, C, D, F, G, H, CRF01 AE, CRF02 AG, CRF12 BF). Group O and HIV-2 isolates have reduced susceptibility in vitro to tipranavir with EC50 values ranging from 0.164-1 µM and 0.233-0.522 µM, respectively. Protein binding studies have shown that the antiviral activity of tipranavir decreases on average 3.75-fold in conditions where human serum is present. Resistance The development of resistance to tipranavir in vitro is slow and complex. In one particular in vitro resistance experiment, an HIV-1 isolate that was 87-fold resistant to tipranavir was selected after 9 months, and contained 10 mutations in the protease: L10F, I13V, V32I, L33F, M36I, K45I, I54V/T, A71V, V82L, I84V as well as a mutation in the gag polyprotein CA/P2 cleavage site. Reverse genetic experiments showed that the presence of 6 mutations in the protease (I13V, V32I, L33F, K45I, V82L, I84V) was required to confer> 10-fold resistance to tipranavir while the full 10-mutation genotype conferred 69-fold resistance to tipranavir. In vitro, there is an inverse correlation between the degree of resistance to tipranavir and the capacity of viruses to replicate. Recombinant viruses showing 3-fold resistance to tipranavir grow at less than 1 % of the rate detected for wild type HIV-1 in the same conditions. Tipranavir resistant viruses which emerge in vitro from wild-type HIV-1 show decreased susceptibility to the protease inhibitors amprenavir, atazanavir, indinavir, lopinavir, nelfinavir and ritonavir but remain sensitive to saquinavir. Through a series of multiple stepwise regression analyses of baseline and on-treatment genotypes from all clinical studies, 16 amino acids have been associated with reduced tipranavir susceptibility and/or reduced 48-week viral load response: 10V, 13V, 20M/R/V, 33F, 35G, 36I, 43T, 46L, 47V, 54A/M/V, 58E, 69K, 74P, 82L/T, 83D and 84V. Clinical isolates that exhibited a 10-fold decrease in tipranavir susceptibility harboured 8 or more tipranavir-associated mutations. In Phase II and III clinical trials, 276 patients with on-treatment genotypes have demonstrated that the predominant emerging mutations with APTIVUS treatment are L33F/I/V, V82T/L and I84V. Combination of all three of these is usually required for reduced susceptibility. Mutations at position 82 occur via two pathways: one from pre-existing mutation 82A selecting to 82T, the other from wild type 82V selecting to 82L.Cross-resistance Tipranavir maintains significant antiviral activity (< 4-fold resistance) against the majority of HIV-1 clinical isolates showing post-treatment decreased susceptibility to the currently approved protease inhibitors: amprenavir, atazanavir, indinavir, lopinavir, ritonavir, nelfinavir and saquinavir. Greater than 10-fold resistance to tipranavir is uncommon (< 2.5 % of tested isolates) in viruses obtained from highly treatment experienced patients who have received multiple peptidic protease inhibitors.Clinical pharmacodynamic data The following clinical data is derived from analyses of 48-week data from ongoing studies (RESIST-1 and RESIST-2) measuring effects on plasma HIV RNA levels and CD4 cell counts. RESIST-1 and RESIST-2 are ongoing, randomised, open-label, multicentre studies in HIV-positive, triple-class experienced patients, evaluating treatment with APTIVUS co-administered with low dose ritonavir (500 mg/200 mg twice daily) plus an optimised background regimen (OBR) individually defined for each patient based on genotypic resistance testing and patient history. The comparator regimen included a ritonavir-boosted PI (also individually defined) plus an OBR. The ritonavir-boosted PI was chosen from among saquinavir, amprenavir, indinavir or lopinavir/ritonavir. All patients had received at least two PI-based antiretroviral regimens and were failing a PI-based regimen at the time of study entry. At least one primary protease gene mutation from among 30N, 46I, 46L, 48V, 50V, 82A, 82F, 82L, 82T, 84V or 90M had to be present at baseline, with not more than two mutations on codons 33, 82, 84 or 90.After Week 8, patients in the comparator arm who met the protocol defined criteria of initial lack of virologic response had the option of discontinuing treatment and switching over to APTIVUS/ritonavir in a separate roll-over study. The 1483 patients included in the primary analysis had a median age of 43 years (range 17-80), were 86 % male, 75 % white, 13 % black and 1 % Asian. In the APTIVUS and comparator arms median baseline CD4 cell counts were 158 and 166 cells/mm3, respectively, (ranges 1-1893 and 1-1184 cells/mm3); median baseline plasma HIV-1 RNA was 4.79 and 4.80 log10 copies/ml, respectively (ranges 2.34-6.52 and 2.01-6.76 log10 copies/ml). Patients had prior exposure to a median of 6 NRTIs, 1 NNRTI, and 4 PIs. In both studies, a total of 67% patient viruses were resistant and 22% were possibly resistant to the pre-selected comparator PIs. A total of 10% of patients had previously used enfuvirtide. Patients had baseline HIV-1 isolates with a median of 16 HIV-1 protease gene mutations, including a median of 3 primary protease gene mutations D30N, L33F/I, V46I/L, G48V, I50V, V82A/F/T/L, I84V, and L90M. With respect to mutations on codons 33, 82, 84 and 90 approximately 4% had no mutations, 24% had mutations at codons 82 (less than 1% of patients had the mutation V82L) and 90, 18% had mutations at codons 84 and 90 and 53% had at least one key mutation at codon 90. One patient in the APTIVUS arm had four mutations. In addition the majority of participants had mutations associated with both NRTI and NNRTI resistance. Baseline phenotypic susceptibility was evaluated in 454 baseline patient samples. There was an average decrease in susceptibility of 2-fold wild type (WT) for tipranavir, 12-fold WT for amprenavir, 55-fold WT for atazanavir, 41-fold WT for indinavir, 87-fold WT for lopinavir, 41-fold WT for nelfinavir, 195-fold WT for ritonavir, and 20-fold WT for saquinavir.Combined 48-week treatment response (composite endpoint defined as patients with a confirmed 1 log RNA drop from baseline and without evidence of treatment failure) for both studies was 34% in the APTIVUS/ritonavir arm and 15% in the comparator arm. Treatment response is presented for the overall population (displayed by enfuvirtide use), and detailed by PI strata for the subgroup of patients with genotypically resistant strains in the Table below. Treatment response* at week 48 (pooled studies RESIST-1 and RESIST-2 in treatment-experienced patients) RESIST study | APTIVUS/RTV | CPI/RTV** | p-value | n (%) | N | n (%) | N | | Overall population FAS PP | 255 (34.2) 171 (37.7) | 746 454 | 114 (15.5) 74 (17.1) | 737 432 | <0.0001 <0.0001 | - with ENF
(FAS) | 85 (50.0) | 170 | 28 (20.7) | 135 | <0.0001 | - without ENF
(FAS) | 170 (29.5) | 576 | 86 (14.3) | 602 | <0.0001 | Genotypically Resistant | | | | | | LPV/rtv FAS PP | 66 (28.9) 47 (32.2) | 228 146 | 23 (9.5) 13 (9.1) | 242 143 | <0.0001 <0.0001 | APV/rtv FAS PP | 50 (33.3) 38 (39.2) | 150 97 | 22 (14.9) 17 (18.3) | 148 93 | <0.0001 0.0010 | SQV/rtv FAS PP | 22 (30.6) 11 (28.2) | 72 39 | 5 (7.0) 2 (5.7) | 71 35 | <0.0001 0.0650 | IDV/rtv FAS PP | 6 (46.2) 3 (50.0) | 13 6 | 1 (5.3) 1 (7.1) | 19 14 | 0.0026 0.0650 | * Composite endpoint defined as patients with a confirmed 1 log RNA drop from baseline and without evidence of treatment failure ** Comparator PI/RTV: LPV/r 400 mg/100 mg twice daily (n=358), IDV/r 800 mg/100 mg twice daily (n=23), SQV/r 1000 mg/100 mg twice daily or 800 mg/200 mg twice daily (n=162), APV/r 600 mg/100 mg twice daily (n=194)ENF Enfuvirtide; FAS Full Analysis Set; PP Per Protocol; APV/rtv Amprenavir/ritonavir; IDV/rtvIndinavir/ritonavir; LPV/rtv Lopinavir/ritonavir; SQV/rtv Saquinavir/ritonavirCombined 48-week median time to treatment failure for both studies was 115 days in the APTIVUS/ritonavir arm and 0 days in the comparator arm (no treatment response was imputed to day 0).Through 48 weeks of treatment, the proportion of patients in the APTIVUS/ritonavir arm compared to the comparator PI/ritonavir arm with HIV-1 RNA < 400 copies/ml was 30% and 14% respectively, and with HIV-1 RNA < 50 copies/ml was 23% and 10% respectively. Among all randomised and treated patients, the median change from baseline in HIV-1 RNA at the last measurement up to Week 48 was -0.64 log10 copies/ml in patients receiving APTIVUS/ritonavir versus -0.22 log10 copies/ml in the comparator PI/ritonavir arm.Among all randomised and treated patients, the median change from baseline in CD4+ cell count at the last measurement up to Week 48 was +23 cells/mm3 in patients receiving APTIVUS/ritonavir (N=740) versus +4 cells/mm3 in the comparator PI/ritonavir (N=727) arm.The superiority of APTIVUS co-administered with low dose ritonavir over the comparator protease inhibitor/ritonavir arm was observed for all efficacy parameters at week 48. It has not been shown that APTIVUS is superior to these boosted comparator protease inhibitors in patients harbouring strains susceptible to these protease inhibitors. RESIST data also demonstrate that APTIVUS co-administered with low dose ritonavir exhibits a better treatment response at 48 weeks when the OBR contains genotypically available antiretroviral agents (eg enfuvirtide).At present there are no results from controlled trials evaluating the effect of APTIVUS on clinical progression of HIV.Paediatric patientsHIV-positive, paediatric patients, aged 2 through 18 years, were studied in a randomized, open-label, multicenter study (trial 1182.14). Patients were required to have a baseline HIV 1 RNA concentration of at least 1500 copies/ml, were stratified by age (2 to < 6 years, 6 to < 12 years and 12 to 18 years) and randomized to receive one of two APTIVUS/ritonavir dose regimens: 375 mg/m2/150 mg/m2 dose, compared to the 290 mg/m2/115 mg/m2 dose, plus background therapy of at least two non-protease inhibitor antiretroviral medicinal products, optimized using baseline genotypic resistance testing. All patients initially received APTIVUS oral solution. Paediatric patients who were 12 years or older and received the maximum dose of 500 mg/200 mg twice daily could change to APTIVUS capsules from study day 28. The trial evaluated pharmacokinetics, safety and tolerability, as well as virologic and immunologic responses through 48 weeks. No data are available on the efficacy and safety of APTIVUS capsules in children less than 12 years of age. Since APTIVUS capsules and oral solution are not bioequivalent, results obtained with the oral solution cannot be extrapolated to the capsules (see also section 5.2). In patients with a body surface area of less than 1.33 m2 appropriate dose adjustments cannot be achieved with the capsule formulation.The baseline characteristics and the key efficacy results at 48 weeks for the paediatric patients receiving APTIVUS capsules are displayed in the tables below. Data on the 29 patients who switched to capsules during the first 48 weeks are presented. Due to limitations in the study design (e.g. non-randomized switch allowed according to patient/clinician decision), any comparisons between patients taking capsules and oral solution are not meaningful.Baseline characteristics for patients 12 18 years of age who took capsuleVariable | Value | Number of Patients | 29 | Age-Median (years) | 15.1 | Gender | % Male | 48.3% | Race | % White | 69.0% | % Black | 31.0% | % Asian | 0.0% | Baseline HIV-1 RNA ( log10
copies/mL) | Median (Min Max) | 4.6 (3.0 6.8) | % with VL > 100,000 copies/mL | 27.6% | Baseline CD4+ (cells/mm3
) | Median (Min Max) | 330 (12 593) | % 200 | 27.6% | Baseline % CD4+ cells | Median (Min Max) | 18.5% (3.1% 37.4%) | Previous ADI* | % with Category C | 29.2% | Treatment history | % with any ARV | 96.6% | | | Median # previous NRTIs | 5 | | | Median # previous NNRTIs | 1 | | | Median # previous PIs | 3 | * AIDS defining illnessKey efficacy results at 48 weeks for patients 12 18 years of age who took capsule Endpoint | Result | Number of patients | 29 | Primary efficacy endpoint: % with VL < 400 | 31.0% | Median change from baseline in log10 HIV-1 RNA (copies/mL) | -0.79 | Median change from baseline in CD4+ cell count (cells/mm3) | 39 | Median change from baseline in % CD4+ cells | 3% |
Analyses of tipranavir resistance in treatment experienced patients APTIVUS/ritonavir response rates in the RESIST studies were assessed by baseline tipranavir genotype and phenotype. Relationships between baseline phenotypic susceptibility to tipranavir, primary PI mutations, protease mutations at codons 33, 82, 84 and 90, tipranavir resistance-associated mutations, and response to APTIVUS/ritonavir therapy were assessed.Of note, patients in the RESIST studies had a specific mutational pattern at baseline of at least one primary protease gene mutation among codons 30N, 46I, 46L, 48V, 50V, 82A, 82F, 82L, 82T, 84V or 90M, and no more than two mutations on codons 33, 82, 84 or 90.The following observations were made:−Primary PI mutations:Analyses were conducted to assess virological outcome by the number of primary PI mutations (any change at protease codons 30, 32, 36, 46, 47, 48, 50, 53, 54, 82, 84, 88 and 90) present at baseline. Response rates were higher in APTIVUS/ritonavir patients than comparator PI boosted with ritonavir in new enfuvirtide patients, or patients without new enfuvirtide. However, without new enfuvirtide some patients began to lose antiviral activity between weeks 4 and 8.−Mutations at protease codons 33, 82, 84 and 90:A reduced virological response was observed in patients with viral strains harbouring two or more mutations at HIV protease codons 33, 82, 84 or 90, and not receiving new enfuvirtide.−Tipranavir resistance-associated mutations:Virological response to APTIVUS/ritonavir therapy has been evaluated using a tipranavir-associated mutation score based on baseline genotype in RESIST-1 and RESIST-2 patients. This score (counting the 16 amino acids that have been associated with reduced tipranavir susceptibility and/or reduced viral load response: 10V, 13V, 20M/R/V, 33F, 35G, 36I, 43T, 46L, 47V, 54A/M/V, 58E, 69K, 74P, 82L/T, 83D and 84V) was applied to baseline viral protease sequences. A correlation between the tipranavir mutation score and response to APTIVUS/ritonavir therapy at week 48 has been established. This score has been determined from the selected RESIST patient population having specific mutation inclusion criteria and therefore extrapolation to a wider population mandates caution.At 48-weeks, a higher proportion of patients receiving APTIVUS/ ritonavir achieved a treatment response in comparison to the comparator protease inhibitor/ritonavir for nearly all of the possible combinations of genotypic resistance mutations (see table below).
Proportion of patients achieving treatment response at Week 48 (confirmed 1 log10 copies/ml decrease in viral load compared to baseline), according to tipranavir baseline mutation score and enfuvirtide use in RESIST patients | New ENF | No New ENF* | Number of TPV Score Mutations** | TPV/r | TPV/r | 0,1 | 73% | 53% | 2 | 61% | 33% | 3 | 75% | 27% | 4 | 59% | 23% | 5
| 47% | 13% | All patients | 61% | 29% | * Includes patients who did not receive ENF and those who were previously treated with and continued ENF**Mutations in HIV protease at positions L10V, I13V, K20M/R/V, L33F, E35G, M36I, K43T, M46L, I47V, I54A/M/V, 58E, H69K, T74P, V82L/T, N83D or I84VENF Enfuvirtide; TPV/r Tipranavir/ritonavirSustained HIV-1 RNA decreases up to week 48 were mainly observed in patients who received APTIVUS/ritonavir and new enfuvirtide. If patients did not receive APTIVUS/ritonavir with new enfuvirtide, diminished treatment responses at week 48 were observed, relative to new enfuvirtide use (see Table below).Mean decrease in viral load from baseline to week 48, according to tipranavir baseline mutation score and enfuvirtide use in RESIST patients | New ENF | No New ENF* | Number of TPV Score Mutations** | TPV/r | TPV/r | 0, 1 | -2.3 | -1.6 | 2 | -2.1 | -1.1 | 3 | -2.4 | -0.9 | 4 | -1.7 | -0.8 | 5
| -1.9 | -0.6 | All patients | -2.0 | -1.0 | * Includes patients who did not receive ENF and those who were previously treated with and continued ENF** Mutations in HIV protease at positions L10V, I13V, K20M/R/V, L33F, E35G, M36I, K43T, M46L, I47V, I54A/M/V, 58E, H69K, T74P, V82L/T, N83D or I84VENF Enfuvirtide; TPV/r Tipranavir/ritonavir−Tipranavir phenotypic resistance:Increasing baseline phenotypic fold change to tipranavir in isolates is correlated to decreasing virological response. Isolates with baseline fold change of>0 to 3 are considered susceptible; isolates with>3 to 10 fold changes have decreased susceptibility; isolates with>10 fold changes are resistant.Conclusions regarding the relevance of particular mutations or mutational patterns are subject to change with additional data, and it is recommended to always consult current interpretation systems for analysing resistance test results. | |