Clinical Pharmacology for Tavneos
Mechanism Of Action
Avacopan is a complement 5a receptor (C5aR) antagonist that inhibits the interaction between C5aR and the anaphylatoxin C5a. Avacopan blocks C5a-mediated neutrophil activation and migration. The precise mechanism by which avacopan exerts a therapeutic effect in patients with ANCA-associated vasculitis has not been definitively established.
Pharmacodynamics
Avacopan blocks the C5a-induced upregulation of CD11b (integrin alpha M) on neutrophils taken from humans dosed with avacopan. The clinical significance of the pharmacodynamic effect is unclear.
Cardiac Electrophysiology
At the approved recommended dose, TAVNEOS does not prolong the QT interval to any clinically relevant extent.
Pharmacokinetics
Based on population pharmacokinetic analysis, the mean steady state plasma exposure estimates of avacopan are 3466 ± 1921 ng•h/mL for the 12-hour area under the plasma drug concentration over time curve (AUC0-12hr) and 349 ± 169 ng/mL for the maximum plasma concentration (Cmax) in patients with ANCA-associated vasculitis receiving 30 mg avacopan twice daily. Steady state plasma levels of avacopan are reached by 13 weeks and the accumulation is approximately 4-fold.
Absorption
Co-administration of 30 mg in capsule formulation with a high-fat, high-calorie meal increases AUC and Cmax of avacopan by approximately 72% and 8%, respectively, and delays tmax by approximately 4 hours (from 2.0 hours to 6.0 hours).
Distribution
The plasma protein binding (e.g., to albumin and α1-acid glycoprotein) of avacopan and metabolite M1 is greater than 99.9%. The apparent volume of distribution of avacopan is estimated to be 345 L.
Elimination
Based on population pharmacokinetic analysis, the estimated total apparent body clearance (CL/F) of avacopan is 16.3 L/h. Following a single dose of 30 mg avacopan with food, the mean elimination half-lives of avacopan and M1 are 97.6 hours and 55.6 hours, respectively, in healthy subjects.
Metabolism
CYP3A4 is the major enzyme responsible for the clearance of avacopan and for the formation and clearance of the major circulating metabolite M1, a mono-hydroxylated product of avacopan. M1 was present at ~12% of the total drug-related materials in plasma and has approximately the same activity as avacopan on the C5aR.
Excretion
The main route of clearance of avacopan is metabolism followed by biliary excretion of the metabolites into feces. Following oral administration of radiolabelled avacopan, about 77% and 10% of the radioactivity was recovered in feces and urine, respectively, and 7% and <0.1% of the radioactive dose was recovered as unchanged avacopan in feces and urine, respectively.
Specific Populations
No clinically significant differences in plasma exposure of avacopan and metabolite M1 were observed based on race (White, Asian, Black), gender (female 31%), age (18 to 83 years), body weight (40.3-174 kg), and renal function (eGFR 14-170 mL/min/1.73m2 at baseline).
Patients With Hepatic Impairment
Mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment had no clinically relevant effect on avacopan and M1 plasma exposure. In subjects with mild or moderate hepatic impairment, avacopan AUC increased by 12% and 12%, respectively, Cmax decreased by 13% and 17%, respectively, compared to subjects with normal liver function. In subjects with mild or moderate hepatic impairment, M1 AUC increased by 11% and 18%, respectively, Cmax decreased by 5% and 16%, respectively, compared to subjects with normal liver function.
TAVNEOS has not been studied in subjects with severe hepatic impairment (Child-Pugh Class C).
Drug Interaction Studies
Effects Of Other Drugs On TAVNEOS
Avacopan is primarily metabolized by CYP3A4. In vitro studies indicate that avacopan is not a substrate of BCRP and P-gp efflux, and OATP1B1 and OATP1B3 uptake transporters. M1 is a substrate of P-gp but is not a substrate of BCRP efflux, and OATP1B1 and OATP1B3 uptake transporters. Summary of results from a clinical study which evaluated the effect of co-administered drugs on avacopan and M1 plasma exposures is shown in Table 2.
Table 2. Changes in Pharmacokinetics of Avacopan and M1 in the Presence of Co-administered Drugs
| Co-administered Drug |
Regimen of Co-administered Drug |
Ratio (90% CI)a |
|
Cmax |
AUC |
Strong CYP3A4 inhibitor:
itraconazole |
200 mg once daily for 4 days |
Avacopan |
1.87
(1.70, 2.06) |
2.19
(2.00, 2.41) |
| M1 |
1.03
(0.95, 1.11) |
1.19
(1.11, 1.28) |
Strong CYP3A4 inducer:
rifampin |
600 mg once daily for 11 days |
Avacopan |
0.21
(0.18, 0.25) |
0.07
(0.06, 0.10) |
| M1 |
0.27
(0.23, 0.31) |
0.07
(0.06, 0.09) |
CI: Confidence interval
a Ratios for Cmax and AUC comparing co-administration of the medication with avacopan vs. administration of avacopan alone. |
Proton-pump inhibitors such as omeprazole are not expected to have a clinically relevant effect on avacopan plasma exposure.
Effect Of TAVNEOS On Other Drug Substances
In vitro studies indicate that avacopan does not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and CYP2D6, and does not induce CYP1A2 and CYP2B6, but shows induction and time-dependent inhibition of CYP3A4. In vitro studies indicate that M1 does not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C19, and CYP2D6, and has a low potential to induce CYP3A4, CYP1A2 and CYP2B6, but may inhibit CYP2C9 and CYP3A4.
In vitro studies indicate that avacopan and M1 do not inhibit the transporters P-gp, BCRP, OATP1B1, OATP1B3, OCT2, OAT1, OAT3, MATE1, and MATE2K at clinically relevant concentrations.
Summary of results from a clinical study which evaluated the effect of avacopan on other drugs is shown in Table 3.
Table 3. Change in Pharmacokinetics of Co-administered Drugs in the Presence of Avacopan
| Co-administered Drug |
Regimen of Avacopan |
Ratio (90% CI)a |
| Cmax |
AUC |
| Sensitive CYP3A4 substrate: simvastatin |
60 mg twice daily for 7 days (fed)b |
3.20
(2.49, 4.10) |
3.53
(3.23, 3.85) |
| Sensitive CYP3A4 substrate: midazolam |
30 mg twice daily for 11 days. (fasted)c |
1.55
(1.41, 1.69) |
1.81
(1.65, 1.98) |
| Sensitive CYP2C9 substrate: celecoxib |
30 mg twice daily for 11 days (fasted)c |
1.64
(1.34, 2.00) |
1.15
(1.03, 1.28) |
CI: Confidence interval
bAvacopan doses were taken with food.
Avacopan systemic exposure represents the therapeutic exposure at steady state with 30 mg twice daily under fed conditions.
c Avacopan doses were taken under fasted conditions. No food was allowed for at least 2 hours post dose for the morning doses. Avacopan systemic exposure was below the therapeutic exposure at steady state with 30 mg twice daily under fed conditions. |
Clinical Studies
The efficacy and safety of TAVNEOS was evaluated in a double-blind, active-controlled, phase 3 clinical trial (NCT02994927) in 330 patients with newly diagnosed or relapsed ANCA-associated vasculitis who were randomized 1:1 to one of the following treatment groups:
- TAVNEOS group (N = 166): Patients received 30 mg avacopan twice daily for 52 weeks plus prednisone-matching placebo for 20 weeks
- Prednisone group (N = 164): Patients received avacopan-matched placebo twice daily for 52 weeks plus prednisone (tapered from 60 mg/day to 0 over 20 weeks)
All patients in both groups received one of the following standard immunosuppressive regimens:
- IV cyclophosphamide 15 mg/kg IV up to 1.2 g maximum every 2 to 3 weeks for 13 weeks followed by oral azathioprine 1 mg/kg/day with titration up to 2 mg/kg/day (or mycophenolate mofetil at a target dose of 2 g/day if azathioprine was contraindicated) from Week 15 onwards
- Oral cyclophosphamide 2 mg/kg/day (maximum 200 mg/day) for 14 weeks followed by azathioprine 1 mg/kg/day with titration up to 2 mg/kg/day (or mycophenolate mofetil at a target dose of 2 g/day if azathioprine was contraindicated) from Week 15 onwards
- IV rituximab 375 mg/m2 once weekly for 4 weeks without azathioprine or mycophenolate mofetil
Glucocorticoids were allowed as pre-medication for rituximab to reduce hypersensitivity reactions, taper after glucocorticoids given during the Screening period, treatment of persistent vasculitis, worsening of vasculitis, or relapses, as well as for non-vasculitis reasons such as adrenal insufficiency.
Randomization was stratified based on 3 factors: newly-diagnosed or relapsing ANCA-associated vasculitis, proteinase 3 positive or myeloperoxidase positive ANCA-associated vasculitis, and standard immunosuppressive regimen. The primary endpoints of the study were disease remission at Week 26 and sustained disease remission at Week 52. Disease remission was defined as achieving a Birmingham Vasculitis Activity Score (BVAS) of 0 and no use of glucocorticoids for treatment of ANCA-associated vasculitis from Week 22 to Week 26. Sustained remission was defined as remission at Week 26 and remission at Week 52, without relapse between Week 26 and Week 52. Remission at Week 52 was defined as BVAS of 0 and no use of glucocorticoids for treatment of ANCA-associated vasculitis from Week 48 to Week 52. Relapse was defined as occurrence of one major item, at least 3 non-major items, or 1 or 2 non-major items for at least 2 consecutive visits on the BVAS after remission (BVAS of 0) had been achieved.
The two treatment groups were well balanced regarding baseline demographics and disease characteristics of patients in this trial. The mean patient age was 60.9 years. Most patients were male (56.4%), Caucasian (84.2%), and had newly diagnosed disease (69.4%). Patients had either GPA (54.8%) or MPA (45.2%) and had presence of anti-PR3 (43.0%) or anti-MPO (57.0%) antibodies. Mean baseline BVAS was 16.2; patients most commonly had manifestations within the renal component (81.2%), general component (68.2%), ear/nose/throat component (43.6%), and chest component (43.0%). Approximately 65% of patients received rituximab, 31% received IV cyclophosphamide, and 4% received oral cyclophosphamide.
Remission At Week 26 And Sustained Remission At Week 52
Remission was achieved by 72.3% of patients in the TAVNEOS group and 70.1% of patients in the prednisone group at Week 26 (treatment difference: 3.4%, 95% CI [-6.0%, 12.8%]). At Week 52, a significantly higher percentage of patients had sustained remission in TAVNEOS group (65.7%) compared to the prednisone group (54.9%), as presented in Table 4.
Table 4. Sustained Remission at Week 52 in Phase 3 Trial (Intent-to-Treat Population)
|
Prednisone
(N = 164)
n (%) |
TAVNEOS
(N = 166)
n (%) |
Estimate of Treatment Difference |
P-valuea |
| Sustained Remission at Week 52 |
90 (54.9%) |
109 (65.7%) |
12.5%b |
0.013 |
| 95% CI |
(46.9, 62.6)c |
(57.9, 72.8)c |
(2.6, 22.3)d |
CI = confidence interval; N = number of patients in the analysis population for the specified treatment group; n = number of patients with disease remission; % = 100*n/N
a 2-sided p-value of Summary Score Test (Agresti 2013)
b Summary Score estimate of the common difference in remission rates (Agresti 2013) by using inverse-variance stratum weights
c Clopper and Pearson exact CI
d Miettinen-Nurminen (Score) confidence limits for the common difference in remission rates |
In pre-specified subgroup efficacy analyses, sustained remission at 52 weeks in patients was examined based on stratification factors and GPA/MPA disease. The results are displayed in Figure 1 below.
Figure 1. Forest Plot of Sustained Remission at Week 52 Based on Disease Related Variables
 |
| AAV = ANCA-associated vasculitis, CYC = cyclophosphamide, GPA = granulomatosis with polyangiitis, MPA = microscopic polyangiitis; MPO = myeloperoxidase positive, PR3 = anti-proteinase 3 positive, and RTX = rituximab. The treatment difference between TAVNEOS and prednisone groups is presented with point estimate and 95% confidence interval using normal approximation. The notation N = XXX/YYY indicates the number of patients randomized who received at least one dose of drug in TAVNEOS arm and prednisone arm, respectively. Subgroup findings should be interpreted with caution due to small sample sizes and overlapping subgroups. |