Double Protease Combinations

Ritonavir + Saquinavir: 60-week update

Dw Cameron, of Ottawa General Hospital and others reported a 60-week update from the Invirase, open label Abbott protocol #462 on the safety, tolerability and antiviral activity of this double protease inhibitor combination. In another study, when ritonavir was combined with the same dose of Invirase or Fortovase, the actual mean plasma exposures were not significantly different (Fortovase package insert). There were 141 participants randomized to one of four dosing regimens: (A) 400 mg bid RTV + 400 mg bid SQV (n=35), every 12 hours; (B) 600 mg bid RTV + 400 mg bid SQV (n=36), every 12 hours; (C) 400 mg tid RTV + 400 mg tid SQV (n=33), every 8 hours; (D) 600 mg bid RTV + 600 mg bid SQV (n=37), every 12 hours.

All participants were protease inhibitor naive and were required to discontinue NRTIs at least two weeks prior to starting study drugs. An average of two antiretroviral drugs was previously used by each of the four treatment groups. Initially, participants received only ritonavir+saquinavir. The median baseline plasma HIV RNA ranged from 4.5 log (31,600 copies/ml) to 4.7 log (50,100 copies/ml) and the baseline median CD4 counts ranged from 266-300 for each of the four groups. All the data reported at the Retrovirus Conference are available on the NATAP web site.

Viral Load and CD4 Changes from Baseline. The week 60 data includes only individuals who remained on study drugs. Study dropouts were not included. It is important to bear in mind that a number of the participants originally randomized to Groups C or D changed their dosing regimens to A or B. After week 12, 27 participants added one or two NRTIs, usually d4T or 3TC (see Table 6). Although data is reported for all four arms, the 400/400 and 600/400 are more widely used in clinical practice. The incidence of side effects is higher in arms C and D. Arms C and D may not be more efficacious than arms A and B. Noncompliance may be higher when using doses used in arms C & D. At week 60, the percentage of individuals who had <200 copies/ml was 82% for the 400+400 bid regimen and 92% for the individuals who were receiving 600 (RTV)+400 (SQV). The CD4 increases were about 170 cells for both groups at week 60.

Ultrasensitive Viral Load. 86% (66/80) of individuals who were <200 copies/ml by the standard assay also had <50 copies/ml using the Ultrasensitive test.

CSF Sub-study. After a year on ritonavir-saquinavir alone, without NRTIs, 15 participants who were <200 copies/ml for at least eight weeks had CSF evaluations. Almost all, 14/15 (93%), had CSF <400 copies/ml. One person on RTV-SQV 600-600 bid had a plasma viral load <200 copies/ml, but had a CSF viral load of 650 copies/ml. Although this data is encouraging, CSF viral load was taken after being on therapy for >1 year. Since there was no CSF evaluation taken prior to study entry, a baseline comparison could not be made. Therefore, it is impossible to measure any actual change. In the Prometheus Study, both baseline and during therapy CSF measures were taken for individuals on RTV/SQV and RTV/SQV plus nucleosides. That data follows.

Safety and Tolerability. Individuals taking the 400+400 bid regimen experienced less incidence of side effects. The severity of side effects should also be less using this regimen, as compared to the 600+400 bid regimen as well as the other regimens. However, if tolerable the 600+400 bid regimen may have a benefit to the 400+400 bid regimen. Using the 600+400 bid regimen results in a higher Cmin for both ritonavir and saquinavir (lowest drug level at 12 hours post dosing). Side effects experienced include: diarrhea, fatigue or malaise, nausea, dizziness, and parasthesia. Parasthesia is a tingling or numbness that can be experienced in the limbs or around the mouth.

The experience of side effects can be reduced by the dose escalation method recommended by Abbott and Roche. Certain dietary recommendations can reduce side effects. Eating high calorie and hi-fat meals at the time of taking the pills can reduce side effects such as, eating a pint of non-low fat yogurt, ice cream or sour cream can reduce side effects. But you may want to balance this with your cholesterol and triglyercides levels. Over time the severity and incidence of side effects tend to diminish for many individuals and a return to a more normal diet is acceptable.

Hepatic Transaminases (Liver Enzymes). Ten of the 14 participants who experienced grade 3 or 4 LFTs (liver function tests) had at least one of the following abnormalities prior to starting study drugs: baseline SGPT (LFTs) above the upper limit of normal; Hepatitis B serum antigen positive; or Hepatitis C antibody positive. Study investigators concluded that liver status prior to treatment with study drugs indicates a potential for elevation of liver enzymes during treatment with study drugs. Individuals with any of the 3 conditions mentioned above (hep B antigen+, hep C antibody+, or elevated LFTs) were more likely to experience grade 3/4 elevations of liver enzymes while taking study drugs. Individuals with a such background should closely monitor LFTs during therapy. Two individuals in each of the 400+400 bid and 600+400 bid regimens experienced grade 3 or 4 elevations of AST and/or ALT. Six persons experienced this in the 600+600 bid regimen.

Some individuals, soon after starting ritonavir+saquinavir regimen, may develop significant elevations in LFTs to the 500-600 level. Rather than immediately discontinuing therapy over concern about those elevations, trying to work through the elevations while continuing on the same regimen with very close monitoring may be successful. The elevations may peak and slowly decrease over time to a manageable level.

Treatment for Elevated Triglycerides and Cholesterol. At week 48, the mean increase from baseline in triglyceride levels for each of the 4 dose regimens ranged from +175 to +290. Participants taking 400+400 bid or 600+400 bid had mean elevations closer to 175. The suggestion is that the 400+400 bid and 600+400 bid regimens are less likely to cause greater increases in triglycerides. 11% (16/141) of patients developed grade 3 or 4 (1500 mg/dl) elevations in triglycerides levels. 6/16 were treated with antihyperlipidemic agents (drugs that may lower triglyceride levels). No cases of pancreatitis have been observed. The antihyperlipidemic drugs used were Atromid, Cofibrate, Atromid-S, and Lopid. The 6 individuals treated had triglyceride levels ranging from 1762 to 3570 prior to intervention. After using the drugs their levels were reduced to from 626 to 1821. The reductions were greater for some individuals than for others. One person had their triglycerides reduced from 3500 to 626, and was treated with Atromid-S . Another person started with 2568, was reduced to 1821, and was treated with Lopid. These drugs are not metabolized by p450 3A4 and should not interact with protease inhibitors.

It is possible that cholesterol levels may be more relevant to future heart related concerns than triglycerides. Data from studies correlate cholesterol with heart disease. The data on correlating triglycerides with heart disease is more mixed. Exercise and diet may play a role in managing elevated lipids for some individuals.

Statin drugs, such as Lovastatin, Simvastatin and a new drug called Pravastatin, are used to lower cholesterol. They may interact with protease inhibitors, but it is uncertain what the interactions are because studies have yet to be conducted. However, the ACTG is discussing plans to study protease statin interactions. The potential concern for interaction is based on a study that found intraconazole hugely increased the blood levels of Simvastatin. Intraconazole did not increase the blood levels so much for Pravastatin, so Pravastatin may be preferable if someone is taking a protease inhibitor. There was a death associated with taking intraconazole with Lovastatin, so there are reasons to be concerned. Based on the effect of intraconzole on statin drugs, protease inhibitors may increase the blood levels of the statin drugs. One way to address that concern is to dose up slowly with the statin drugs. It is not believed that the statin drugs effect blood levels of the protease inhibitors.

Treatment Intensification. During the study, 27 patients had to add up to two NRTIs after week 12 for virologic failure or incomplete suppression. D4T/3TC were used by 23/27 (85%) of the patients, who were <200 copies/ml after intensification and remained at that level at week 60.

Correlation of Compliance with Treatment Response at Week 24. In the week 24 data report, the investigators reported a compliance assessment of participants up to week 24. They concluded that compliance is highly correlated with treatment response. At week 24, 90% of those defined as being compliant were <200 copies/ml and 97% of those were <1000 copies/ml. Only 66% defined as non-compliant were <200 copies/ml and only 73% were <1000 copies/ml. See the actual report for the investigators definition of compliance.

Viral Load Reduction at Week 12 Predicts Treatment Response at Week 24. This report also was issued at week 24. Investigators showed data that individuals with <1001 copies/ml at week 12, 98% had <200 copies at week 24. Also, only 25% of those who had a viral load of <200 copies/ml at week 24 had >1000 copies/ml at week 12. If an individual’s viral load was <201 copies/ml at week 12, 93% were <200 copies/ml at week 24. At Chicago Retrovirus Conference, Lisa Demeter reported that data from ACTG 320 indinavir clinical endpoint study indicates that early viral load reductions also predicted treatment response. Intensification of treatment could be considered at, for example, 12 weeks.

The Effect on CSF Viral Load of RTV/SQV and RTV/SQV+d4T in the Prometheus Study

NATAP previously reported preliminary data from the Prometheus Study that was presented at the Hamburg AIDS Conference. A 24-week update was reported in Chicago. Investigators reported CSF viral load changes between week 0 and week 12 for eight individuals receiving RTV/SQV alone and for nine individuals receiving RTV/SQV+d4T. Unlike the CSF data above, this has a comparison between two time points (weeks 0 and 12).

Viral Load and CD4 Response. In this open label study, 138 participants were randomized to receive either RTV/SQV (400 mg bid of both) or RTV/SQV+d4T. The mean baseline CD4 was 273 and 251 for protease alone and d4T arms, respectively. Mean baseline HIV RNA was 4.3 log (about 20,000 copies/ml) for both arms. Also, 54% in protease alone arm had previous NRTI experience while 47% in d4T arm had previous NRTI experience. At week 24, 64% taking RTV/SQV alone and 87% taking RTV/SQV/d4T were <400 copies/ml (total # of evaluable patients at week 24 is111). If viral load did not reach undetectable by week 18, intensification was permitted. Six patients in the RTV/SQV arm intensified with d4T/3TC and all six were undetectable by week 36. Mean CD4 increase was about +145 for both arms.

CSF Substudy. Of the 28 patients who volunteered for the substudy, 17 completed 12 weeks. Lumbar punctures were performed before the start of study (week 0) and after 12 weeks (week 12).

Of the patients with detectable viral load in serum and CSF at week 0, and undetectable viral in serum at week 12, 1/3 on RTV/SQV alone arm and 4/5 in the RTV/SQV/d4T arm had an undetectable CSF viral load at week 12. Three out of five receiving RTV+SQV alone had reductions in CSF viral load at week 12; however, week 12 may be too soon to evaluate the effect of a therapy on CSF viral load. In the CSF evaluation where 14/15 had undetectable CSF viral load, the CSF viral load levels were assessed after one year of therapy. The authors said that neither ritonavir nor saquinavir was found to penetrate the CSF well in nine patients as measured by RTV or SQV CSF drug levels. Keep in mind that ritonavir is 99% protein bound in blood and it is difficult to find unbound ritonavir in blood.

Nelfinavir + Saquinavir

There were updated reports from two studies of this combination at the Retrovirus Conference. NATAP Reports’ January ‘98 issue reported the updates that were presented in Hamburg at the European AIDS Conference in November ‘97. More extensive data reports and discussions are available on the NATAP web site. The following report will present the latest information made available in Chicago. The Kravick study is a small open label evaluation of 14 individuals receiving NFV 750mg tid (3X/day) and SQV 800mg tid (3X/day). Nelfinavir increases SQV SGC AUC (blood levels) by 5 fold. Saquinavir does not significantly effect NFV blood levels. SQV 800mg tid was selected by Roche for both of the studies discussed here. Participants in this study were both NRTI naive (n=3) and experienced (n=11), but protease na´ve. Some took NRTIs with the NFV/SQV therapy while others received only the NFV/SQV combination. The initial part of the study was a pharmacokinetic evaluation following which all participants were maintained on NFV 750 mg tid + SQV SGC 800 mg tid with the possible addition or continuation of up to two NRTIs.

Viral Load and CD4 Changes. The median baseline HIV RNA was 39,917 copies/ml (range 19,496 - 109,065). The median CD4 count was 327 cells (range 19-621). At month 12, the median decrease in HIV RNA was about 2.4 log (n=9) and the median increase in CD4 was about 100 (the increase at month 11 was 172), n=9. 80% of the patients were <500 copies/ml was at month 12 (n=9), while 90% were at that level at month 11. As you can see, the data is based on a small number of individuals. The CD4 increases, viral load changes, and mutations developed while on study medications for each participant is available on the NATAP web site.

M. Opravil and others reported the second study called SPICE and is a pilot randomized study enrolling 157 individuals comparing four following treatment arms: SGC SQV 1200 mg tid + 2 NRTIs (A), n=26;NFV 750 mg tid + 2 NRTIs (B), n=26; SQV SGC 800 mg tid + NFV 750 mg tid + 2 NRTIs (C), n=51; SQV SGC 800 mg tid + NFV 750 mg tid without NRTIs (D), n=54.

Crossovers to the 4-drug regimen were permitted for intolerance or virological failure. Participants had to be able to start at least one new NRTI. The study investigators said the data should be considered preliminary until formal analysis at week 48. The baseline mean CD4 counts were about 310 for each of the four arms. The mean baseline viral load ranged from 50,000 to 63,000 for the four arms. It is difficult to sort out the true treatment effect of each of the different regimens used in this study, except for the 4-drug arm. About 46% of the participants in the three arms using NRTIs had prior NRTI experience. At the start of the study, 17% to 25% of the individuals in the three arms initially receiving NRTIs received two new NRTIs. These variables complicate trying to characterize the true treatment effect of each arm in comparison to the other arms. However, the one double protease arm of nelfinavir+saquinavir does not suffer from this concern because no NRTIs were initially used.

Of the 54 individuals initially randomized to receive nelfinavir+ saquinavir alone, 11 changed therapies for virologic failure. Of the 51 individuals randomized to receive nelfinavir+saquinavir+2 NRTIs, no one changed therapy due to virologic failure. One person experienced a serious diabetes related adverse event.

Preliminary Week 32 Changes in Viral Load and CD4 from Baseline. By 32 weeks, 24 patients crossed over to NFV+SQV+2 NRTIs (C). Six crossed over for toxicity and 18 for virologic failure (2 from arm A, 5 from arm B and 11 from arm D). The authors said 11 additional patients were defined as virologic failures but had not yet crossed over at the time of this analysis. Since a number of individuals crossed over to the 4-drug double protease arm from the other three arms, the CD4 increases and viral load reductions for the persons in those arms are not very relevant at this point. However, of the 51 individuals initially randomized to nelfinavir+saquinavir+2 NRTIs, 53% had previous NRTI experience, as did all the other treatments arms. For these 51 individuals initially randomized to the 4 drug arm, CD4 increases were +134, 83% had <400 copies/ml, 70% had <50 copies/ml, and the viral load reduction was -2.46 log using the Ultrasenstive test and -1.75 log using the 400 copies/ml test at week 32.

Indinavir + Nelfinavir

In preliminary studies conducted by Agouron, reseachers found that in a single dose study, drug blood levels to both indinavir and nelfinavir increased compared to monotherapy with each drug. In the interest of potentially increasing potency and decreasing dosing from three times per day to two times per day (for both drugs), this pilot study of combining IDV with NFV was initiated.

Initially, 21 patients were enrolled in this study. The median baseline viral load was 50,500 copies/ml (range 9000-316,170) and the median baseline CD4 was 259 (range 120-568). Furthermore, 58% had no prior antiretroviral experience and the remaining 42% were NRTI experienced.

Group A received NFV 500mg every 12 hrs + IDV 1000 mg every 12 hrs (q12h) for one week. Starting in the second week, they received NFV 750 mg q12h + IDV 1000 mg q12h. Group B started with NFV 750 mg q12h + IDV 1000 mg q12h.

Based on the data from Agouron’s single dose studies, it was expected that those effects seen in that study (increased IDV AUC by 51%-single dose of IDV; increased NFV AUC by 83%-single dose of NFV) would be seen when combining NFV with IDV. The investigators in this study did not observe those PK responses reflected in this study. This indicates that you cannot generally rely upon single or limited dosing studies to predict drug interactions and optimal dosing regimens. To do so is risky. It is safer to wait for additional research identifying adequate dosing regimens.

Investigators in this study found that when combining 1000mg IDV q12h with 750mg NFV q12h, indinavir blood levels were similar to indinavir taken at the standard dosing of 800 mg every 8 hours. Indinavir did not increase NFV steady state blood levels, resulting in low NFV trough levels. At week eight, 7/10 study participants were <500 copies/ml, and nine patients had a mean increase in CD4 of 156 cells. Treatment was discontinued in one person for rash. Other adverse events included diarrhea/loose stools (6), bloating (4), and nephrolithiasis or kidney stones (2). Because of the low NFV trough levels, a higher dose of nelfinavir was investigated. All participants raised their dose of nelfinavir from 750 to 1000 mg q12h, while maintaining IDV dosing at 1000mg q12h.

For an explanation of terms like trough, AUC, Cmax and pharmacokinetics see the report titled Primer on PK on the NATAP web site.

The investigators reported the mean percent change in NFV PK resulting from increase in NFV dose of 750 mg q12h to 1000 mg q12h in AUC, Cmax and trough for the five patients studied was 31%, 27%, and 35%, respectively.

In the study, 10/21 (47%) had undetectable HIV RNA by the Roche Amplicor viral load test (<400 copies/ml). Six of the 10 were undetectable using the Roche ultrasensitive test (<50 copies/ml). Three study participants added NRTIs to their regimen after at least 12 weeks either for virological failure or to increase antiviral effect to prevent virological failure. The median increase in CD4 from baseline (12-32 weeks) was 133 cells. There were five discontinuations. Viral Load changes for the 21 participants and the actual PK data are available on the NATAP web site.

The antiviral activity or potency of the combination might improve if the dosing of indinavir and/or nelfinavir were increased to the dosing regimens used in their bid studies (1200mg bid for NFV and 1250mg bid for IDV). A potential concern might be the increase of side effects such as diarrhea from NFV or nephrolithiasis from IDV. Authors concluded the optimal role of IDV/NFV twice daily dosing will be clarified by ongoing studies using additional dosing regimens and potential future studies evaluating the addition of NRTIs and NNRTIs to this combination.

Adverse Events. Six individuals reported grade 2 or higher diarrhea, and 4 persons reported grade 2 or higher bloating/cramps. Two persons reported nephrolithiasis (kidney stones) and one of those two reported two incidences of nepthrolithiasis.

Nelfinavir+Ritonavir

Testing of this combination is in early stages. Two small initial pilot studies are ongoing exploring different dosing regimens of these two protease inhibitors. One study is exploring 400 mg ritonavir bid + 1000 mg nelfinavir + d4T/3TC. This study has just started, so it will be a while before data will be available. Investigators are examining the effect of therapy on CSF and lymph tissue, as well as performing immunological evaluations.

In Chicago, JE Gallant and C. Flexner of Johns Hopkins and others reported preliminary findings from a small open-label, dose escalating, non-randomized trial in 20 individuals. Participants were protease inhibitor na´ve, while 10 were NRTI experienced and 10 were NRTI na´ve. All were permitted to add NRTIs after week 12 at the discretion of the investigator. The study is an initial assessment of safety, pharmacokinetics and antiviral activity of two dosing regimens (400mg RTV bid+500mg NFV bid, 400mg RTV bid+750mg NFV bid).

Viral Load and CD4 Changes. The median baseline HIV RNA and CD4 for all 20 patients were 32,459 (range 4,118->750,000 copies/ml) and 325 cells (range 23-941), respectively. The 20 participants were divided into two groups. Group one received 500mg NFV bid with 400mg RTV bid while group two received 750mg NFV bid with 400mg RTV bid. Each group dose escalated for several days before reaching the full dose regimens.

The Group 1 mean baseline HIV RNA was 58,045 copies/ml (range 4,912 to 279,938) and mean baseline CD4 was 335 (range 29-1042). Five people in Group 1 were treatment naive and five were experienced. The Group 2 mean baseline HIV RNA was 135,300 copies/ml 7,756-939,794). Mean baseline CD4 was 329 (range 186-578). Five people in Group 2 were treatment naive and five were experienced.

Current Status of Group 1 (500mg NFV): Six of ten achieved <400 copies/ml and 2/10 were <20 copies/ml before adding NNRTIs. Four patients discontinued because of virologic failure (>1 log increase in viral load on 2 consecutive visits). Failures occurred during weeks 6 to 8 for one person, weeks 12 to 14 for another. One person (HIV RNA 20-400 copies/ml) added two NRTIs (d4T/3TC for one, AZT/3TC for two) at weeks 16 (n=1) and 20 (n=2) while another individual with undetectable viral load (HIV RNA <20 copies/ml) added AZT/3TC at week 24. A person with low but detectable viral load (HIV RNA 20-400 copies/ml at weeks 20 and 24) remained on RTV/NFV without adding NRTIs. One individual is temporarily off the study due to incarceration, but had HIV RNA <20 copies/ml at week 12 prior to treatment interruption.

Current Status of Group 2: Of the test group, 6/10 achieved <400 copies/ml and 3/10 were <20 copies/ml before adding NRTIs or NNRTI. Two persons with undetectable viral loads (HIV RNA <20 copies/ml) added NRTIs at week 16 (d4T/3TC for one, NVP/3TC for other). Three persons with low but detectable virus (HIV RNA 20-400 copies/ml) added NRTIs at week 16 (AZT/3TC for 2 and d4T/3TC for 1). Three people with detectable viral load (HIV RNA >400 copies/ml) also added NRTIs at week 16 (d4T/ddI in 2, d4T/3TC in 1). One individual with undetectable viral load (HIV RNA <20 copies/ml) at week 16 remained on NFV/RTV without adding NRTIs. Finally, one person with 2 episodes of noncompliance and alcohol abuse (4-day drug holiday at week 10 and 3 day drug holiday at week 16) has withdrawn from study.

Genotypic mutations are being assessed in persons experiencing failure. Nine people reported moderate to severe diarrhea, four reported nausea and three reported malaise or fatigue.

141W94 (Amprenavir) in Combination with NFV, SQV or IDV

Joe Eron, of UNC, reported on the preliminary findings from PROA2001, a small phase II open label study. The study’s goal is to evaluate the efficacy of 141 in combination with other protease inhibitors for the purpose of identifying which combinations to explore further and to examine steady state pharmacokinetics for each combination. Using data from previous research, investigators have characterized a preliminary range for increases in Cmax of 16-31% and in AUC of 22-64% for 141 when used with indinavir. They reported no appreciable change in indinavir blood levels when used with 141 and sought to assess safety and tolerability.

Participants are protease na´ve, but could be NRTI experienced. If so, they washed out medications prior to receiving study drugs. After 12 weeks, patients can add NRTIs if their viral load is >400 copies/nl, but so far no one has exercised that option. Patients tolerating study drugs could continue out to 48 weeks. At baseline, the median CD4 was 393 (n=33) and the median viral load was 42,600 copies/ml. There were 21 participants who had prior NRTI experience and most had minimal or no symptoms.

Preliminary Viral Load Data. The number of patients starting therapy in each arm is small and the number of evaluable participants at week 16 is even smaller. Therefore, results are very preliminary. There were two serious adverse events resulting in two dropouts. Because the number of participants is so small, it is difficult to distinguish significant differences between the arms and it is difficult to draw conclusions. After 3 weeks, AZT/3TC was added to 141 monotherapy in the 4th arm. See Table 25

Most Common Adverse Events by Regimen. Nine of 34 patients discontinued study drugs due to consent withdrawal, lost to follow-up, or serious adverse events. See Table 26

 

Table 25. 141W94 Double Protease Combinations - Week 16 Viral Load Changes

Table 26. Adverse Events - 141W94 Double Protease Combinations