Clinical Pharmacology for Oxlumo
Mechanism Of Action
Lumasiran reduces levels of glycolate oxidase (GO) enzyme by targeting the hydroxyacid oxidase 1 (HAO1) messenger ribonucleic acid (mRNA) in hepatocytes through RNA interference. Decreased GO enzyme levels reduce the amount of available glyoxylate, a substrate for oxalate production. As the GO enzyme is upstream of the deficient alanine: glyoxylate aminotransferase (AGT) enzyme that causes PH1, the mechanism of action of lumasiran is independent of the underlying AGXT gene mutation. OXLUMO is not expected to be effective in primary hyperoxaluria type 2 (PH2) or type 3 (PH3) because its mechanism of action does not affect the metabolic pathways causing hyperoxaluria in PH2 and PH3.
Pharmacodynamics
The pharmacodynamic effects of OXLUMO have been evaluated in adult and pediatric patients with PH1 across a range of doses and dosing frequency. Dose-dependent reductions in urinary oxalate levels were observed, resulting in the selection of the recommended body weight-based loading and maintenance dosing regimens. With the recommended dosing regimens, onset of effect was observed within two weeks after the first dose and maximal reductions in urinary oxalate were observed by Month 2 and persisted with continued use of OXLUMO maintenance dosage [see Figures 1 and 2 in Clinical Studies].
Cardiac Electrophysiology
At the recommended dose, OXLUMO does not lead to clinically relevant QT interval prolongation.
Pharmacokinetics
The pharmacokinetic (PK) properties of OXLUMO were evaluated following administration of single and multiple dosages in patients with PH1 as summarized in Table 3.
Table 3: Pharmacokinetic Parameters of Lumasiran
|
Lumasiran |
| General Information |
| Steady-State Exposure |
Cmax [Median (Range)] |
462 (38.5 to 1500) ng/mL |
| AUC0-last [Median (Range)] |
6810 (2890 to 10700) ng-h/mL |
| Dose Proportionality |
- Lumasiran exhibited an approximately dose proportional increase in plasma exposure following single subcutaneous doses ranging from 0.3 to 6 mg/kg.
- Lumasiran exhibited time-independent pharmacokinetics with multiple doses of 1 and 3 mg/kg once monthly or 3 mg/kg quarterly.
|
| Accumulation |
- No accumulation of lumasiran was observed in plasma after repeated monthly or quarterly dosing.
|
| Absorption |
| Tmax [Median (Range)] |
4 (0.5 to 12) hours |
| Distributiona |
| Estimated Vd/F |
4.9 L |
| Protein Binding |
85% |
| Elimination |
| Apparent Half-Life [Mean (%CV)] |
5.2 (47%) hours |
| Estimated CL/F |
26.5 L/hour |
| Metabolism |
| Primary Pathway |
Lumasiran is metabolized by endo- and exonucleases to oligonucleotides of shorter lengths. |
| Excretion |
| Primary Pathway |
Less than 26% of the administered dose of lumasiran is excreted unchanged into the urine within 24 hours with the rest excreted as inactive metabolite. |
a Lumasiran distributes primarily to the liver after subcutaneous administration.
Cmax = maximum plasma concentration; AUC0-last = area under the plasma concentration-time curve from time of administration (0) to the last measurable time point (last); Tmax = time to maximum concentration; Vd/F = apparent volume of distribution; CV = coefficient of variation; CL/F = apparent clearance. |
Specific Populations
No clinically significant differences in the pharmacokinetics or pharmacodynamics of lumasiran were observed based on age (4 months to < 65 years old), sex, race/ethnicity, renal impairment, use of hemodialysis, or mild to moderate hepatic impairment (total bilirubin ≤ULN and AST > ULN; or total bilirubin ≤ 3 x ULN). The effect of severe hepatic impairment on the pharmacokinetics of lumasiran is unknown.
Body Weight
In children < 20 kg, lumasiran Cmax was twice as high due to the higher 6 mg/kg dose and faster absorption rate. At the approved recommended dosage, lumasiran AUC was similar across the 6.2 kg to 110 kg body weight range [see DOSAGE AND ADMINISTRATION].
Drug Interaction Studies
Clinical Studies
No clinical studies evaluating the drug interaction potential of lumasiran have been conducted. Concomitant use of pyridoxine (vitamin B6) did not influence the pharmacodynamics or pharmacokinetics of lumasiran.
In Vitro Studies
In vitro studies indicate that lumasiran is not a substrate or an inhibitor of cytochrome P450 (CYP) enzymes. Lumasiran is not expected to induce CYP enzymes or modulate the activities of drug transporters.
Immunogenicity
The observed incidence of anti-drug antibody (ADA, including neutralizing antibody) is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of ADA in the studies described below with the incidence of ADA in other studies, including those of OXLUMO or of other siRNA products.
Across all clinical studies in the lumasiran development program, including patients with PH1 and healthy volunteers dosed with OXLUMO, 7 of 120 (6%) lumasiran-treated individuals with mean follow-up duration of 8.9 months, tested positive for ADA, as early as from Day 29.
No clinically significant differences in the safety, pharmacokinetic, or pharmacodynamic profiles of lumasiran were observed in patients who tested positive for ADA.
Clinical Studies
ILLUMINATE-A
ILLUMINATE-A was a randomized, double-blind trial comparing lumasiran and placebo in 39 patients 6 years of age and older with PH1 and an eGFR ≥ 30 mL/min/1.73 m² (ILLUMINATE-A; NCT03681184). Patients received 3 loading doses of 3 mg/kg OXLUMO (N = 26) or placebo (N = 13) administered once monthly, followed by quarterly maintenance doses of 3 mg/kg OXLUMO or placebo [see DOSAGE AND ADMINISTRATION]. After six months, all patients received OXLUMO.
The median age of patients at first dose was 15 years (range 6 to 61 years), 67% were male, and 77% were White. At baseline, the median 24-hour urinary oxalate excretion corrected for body surface area (BSA) was 1.7 mmol/24 h/1.73 m², the median plasma oxalate level was 13.1 μmol/L, 33% of patients had eGFR ≥ 90 mL/min/1.73 m² , 49% had eGFR of 60 to < 90 mL/min/1.73 m², and 18% had eGFR 30 to < 60 mL/min/1.73 m² , 56% were on pyridoxine, and 85% reported a history of symptomatic kidney stone events.
The primary endpoint was the percent reduction from baseline in 24-hour urinary oxalate excretion corrected for BSA averaged over Months 3 through 6. The LS mean percent change from baseline in 24-hour urinary oxalate in the OXLUMO group was -65% (95% CI: -71, -59) compared with -12% (95% CI: -20, -4) in the placebo group, resulting in a between-group LS mean difference of 53% (95% CI: 45, 62; p < 0.0001) [Figure 1].
Figure 1: ILLUMINATE-A: Percent Change from Baseline in 24-hour Urinary Oxalate by Month
By Month 6, 52% (95% CI: 31, 72) of patients treated with OXLUMO achieved a normal 24-hour urinary oxalate corrected for BSA (≤ 0.514 mmol/24 hr/1.73 m²) compared to 0% (95% CI: 0, 25) placebo-treated patients (p = 0.001). Reduced urinary oxalate levels were maintained through Month 24 in patients treated with OXLUMO.
ILLUMINATE-B
ILLUMINATE-B was a single-arm study in 18 patients <6 years of age with PH1 and an eGFR > 45 mL/min/1.73 m² for patients ≥ 12 months of age or a normal serum creatinine for patients < 12 months of age (ILLUMINATE-B; NCT03905694). Dosing was based on body weight [see DOSAGE AND ADMINISTRATION].
The median age of patients at first dose was 51 months (range 4 to 74 months), 56% were female, and 88% were White. Three patients were less than 10 kg, 12 were 10 kg to < 20 kg, and 3 were ≥ 20 kg. The median spot urinary oxalate: creatinine ratio at baseline was 0.47 mmol/mmol.
The primary endpoint was the percent reduction from baseline in spot urinary oxalate: creatinine ratio averaged over Months 3 through 6. Patients treated with OXLUMO achieved a reduction in spot urinary oxalate: creatinine ratio from baseline of 72% (95% CI: 66, 78) (Figure 2). The reduction in urinary oxalate excretion was maintained with continued OXLUMO treatment through Month 12.
Figure 2: ILLUMINATE-B: Percent Change from Baseline in Spot Urinary Oxalate: Creatinine Ratio by Month
Abbreviation: CI = Confidence Interval.
Results are plotted as mean (95% CI) of percent change from baseline.
ILLUMINATE-C
A total of 21 patients were enrolled and treated with OXLUMO in a multi-center, single-arm study in patients with PH1 and an eGFR ≤ 45 mL/min/1.73 m² in patients 12 months of age and older or an elevated serum creatinine for age in patients less than 12 months of age, including patients on hemodialysis. ILLUMINATE-C included 2 cohorts. Cohort A included 6 patients who did not require dialysis at the time of study enrollment. Cohort B included 15 patients who were on a stable regimen of hemodialysis; the hemodialysis regimen was to remain stable in these patients for the first 6 months of the study. Patients received the recommended dosing regimen of OXLUMO based on body weight [see DOSAGE AND ADMINISTRATION]. Patients requiring peritoneal dialysis were excluded.
The median age of patients at first dose was 9 years (range 0 to 59 years), 57% were male, and 76% were White. For Cohort A, the median plasma oxalate level was 58 μmol/L. For Cohort B, the median pre-dialysis plasma oxalate level was 104 μmol/L.
The primary endpoint was the percent change in plasma oxalate from baseline to Month 6 (average from Month 3 to Month 6) for Cohort A (N = 6) and the percent change in pre-dialysis plasma oxalate from baseline to Month 6 (average from Month 3 to Month 6) for Cohort B (N = 15). The percent change from baseline to Month 6 in plasma oxalate levels in Cohort A was an LS mean difference of -33% (95% CI: -82, 15) and in Cohort B was -42% (95% CI: -51, -34).
Mean plasma oxalate decreased from 65 μmol/L (95% CI: 21, 108) at baseline to 33 μmol/L (95% CI: 10, 56) at Month 6 in Cohort A, and from 108 μmol/L (95% CI: 92, 125) at baseline to 62 μmol/L (95% CI: 51, 72) at Month 6 in Cohort B. The time course for changes in plasma oxalate is shown in Figure 3.
Figure 3: ILLUMINATE-C: Plasma Oxalate Levels (μmol/L) during the Primary Analysis Period by Month
Abbreviation: CI = Confidence Interval.
Results are plotted as mean (95% CI) of actual values.
For Cohort A, the baseline is defined as the mean of all plasma oxalate samples collected prior to the first dose of lumasiran; for Cohort B, the baseline is defined as the last four pre-dialysis plasma oxalate samples collected prior to the first dose of lumasiran. In Cohort B, only pre-dialysis samples are utilized.