CLINICAL PHARMACOLOGY
Mechanism Of Action
Golodirsen is designed to bind
to exon 53 of dystrophin pre-mRNA resulting in exclusion of this exon during
mRNA processing in patients with genetic mutations that are amenable to exon 53
skipping. Exon 53 skipping is intended to allow for production of an internally
truncated dystrophin protein in patients with genetic mutations that are
amenable to exon 53 skipping [see Clinical Studies].
Pharmacodynamics
After treatment with VYONDYS
53, all patients evaluated (n=25) in Study 1 Part 2 [see Clinical Studies]
had an increase in skipping of exon 53 demonstrated by reverse transcription
polymerase chain reaction (RT-PCR), compared to baseline.
In Study 1 Part 2 [see Clinical
Studies], dystrophin levels increased from 0.10% (SD 0.07) of normal at
baseline to 1.02% (SD 1.03) of normal after 48 weeks of treatment with VYONDYS 53.
The mean change from baseline in dystrophin after 48 weeks of treatment with
VYONDYS 53 was 0.92% (SD 1.01) of normal levels (p<0.001); the median
change from baseline was 0.88%. This increase in dystrophin protein expression
positively correlated with the level of exon skipping. Correct localization of
truncated dystrophin to the sarcolemma in muscle fibers of patients treated
with golodirsen was demonstrated by immunofluorescence staining.
Pharmacokinetics
The pharmacokinetics of golodirsen was evaluated in DMD
patients following administration of intravenous doses ranging from 4
mg/kg/week to 30 mg/kg/week (i.e., recommended dosage). Golodirsen exposure
increased proportionally with dose, with minimal accumulation with once-weekly
dosing. Inter-subject variability (as %CV) for Cmax and AUC ranged from 38% to
72%, and 34% to 44%, respectively.
Distribution
Steady-state volume of distribution was similar between
DMD patients and healthy subjects. The mean golodirsen steady-state volume of
distribution was 668 mL/kg (%CV=32.3) at a dose of 30 mg/kg. Golodirsen plasma
protein binding ranged from 33% to 39% and is not concentration dependent.
Elimination
Golodirsen elimination half-life (SD) was 3.4 (0.6)
hours, and plasma clearance was 346 mL/hr/kg at the 30 mg/kg dose.
Metabolism
Golodirsen is metabolically stable. No metabolites were
detected in plasma or urine.
Excretion
Golodirsen is mostly excreted unchanged in the urine. The
elimination half-life (t½) was 3.4 hours.
Specific Populations
Age
The pharmacokinetics of golodirsen have been evaluated in
male pediatric DMD patients. There is no experience with the use of VYONDYS 53
in DMD patients 65 years of age or older.
Sex
Sex effects have not been evaluated; VYONDYS 53 has not
been studied in female patients.
Race
The potential impact of race is not known because 92% of
the patients in studies were Caucasians.
Patients With Renal Impairment
The effect of renal impairment on the pharmacokinetics of
golodirsen was evaluated in non-DMD subjects aged 41 to 65 years with Stage 2
chronic kidney disease (CKD) (n=8, estimated glomerular filtration rate (eGFR)
≥60 and <90 mL/min/1.73 m²) or Stage 3 CKD (n=8, eGFR ≥30 and
<60 mL/min/1.73 m²) and matched healthy subjects (n=8, eGFR ≥90
mL/min/1.73 m²). Subjects received a single 30 mg/kg IV dose of golodirsen.
In subjects with Stage 2 or Stage 3 CKD, exposure (AUC)
increased approximately 1.2-fold and 1.9-fold, respectively. There was no
change in the Cmax in subjects with Stage 2 CKD; in subjects with Stage 3 CKD,
there was a 1.2-fold increase in Cmax compared with subjects with normal renal
function. The effect of Stage 4 or Stage 5 CKD on golodirsen pharmacokinetics
and safety has not been studied.
Estimated GFR values derived from MDRD equations and the
threshold definitions for various CKD stages in otherwise healthy adults would
not be generalizable to pediatric patients with DMD. Therefore, no specific
dosage adjustment can be recommended for patients with renal impairment [see
Use In Specific Populations].
Patients With Hepatic Impairment:
VYONDYS 53 has not been studied in patients with hepatic
impairment.
Drug Interaction Studies
Golodirsen did not inhibit CYP1A2, CYP2B6, CYP2C8,
CYP2C9, CYP2C19, CYP2D6, or CYP3A4/5 in vitro. Golodirsen was a weak inducer of
CYP1A2 and did not induce CYP2B6 or CYP3A4. Golodirsen was not metabolized by
human hepatic microsomes and was not a substrate or strong inhibitor of any of
the key human drug transporters tested (OAT1, OAT3, OCT2, OATP1B1, MATE1, P-gp,
BCRP, and MRP2, OATP1B3 and MATE2-K). Based on in vitro data, golodirsen has a
low potential for drug-drug interactions in humans.
Animal Toxicology And/Or Pharmacology
Kidney toxicity was observed in studies in male mice and
rats; findings in urinary bladder were observed in male mice.
In male mice, golodirsen was administered weekly for 12
weeks by intravenous injection (0, 12, 120, or 960 mg/kg) or for 26 weeks by
subcutaneous injection (0, 120, 300, or 600 mg/kg). In the 12-week study,
microscopic findings in kidney (tubular dilatation, basophilic or eosinophilic
casts, vacuolation), correlated with increases in serum markers of renal
function (e.g., urea nitrogen, creatinine), were observed primarily at the
highest dose tested; hypertrophy of the transitional epithelium of the ureter
or urinary bladder was observed at all doses. In the 26-week study, renal
tubular degeneration and degeneration of the transitional epithelium of the
urinary bladder were observed at all doses.
In male rats, intravenous administration of golodirsen
(0, 60, 100, 300, or 600 mg/kg) weekly for 13 weeks resulted in tubular
degeneration at all but the lowest dose tested; at the high dose, the
microscopic changes were accompanied by increases in serum urea nitrogen.
In male monkeys, intravenous administration of golodirsen
(0, 80, 200, or 400 mg/kg) weekly for 39 weeks resulted in microscopic changes
in kidney (basophilia, dilatation, or mononuclear cell infiltration) at all
doses, which correlated with increases in serum markers of renal function (urea
nitrogen, creatinine) at the highest dose tested.
Clinical Studies
The effect of VYONDYS 53 on dystrophin production was
evaluated in one study in DMD patients with a confirmed mutation of the DMD gene
that is amenable to exon 53 skipping (Study 1; NCT02310906).
Study 1 Part 1 was a double-blind, placebo-controlled,
dose-titration study in 12 DMD patients. Patients were randomized 2:1 to
receive VYONDYS 53 or matching placebo. VYONDYS 53treated patients received
four escalating dose levels, ranging from 4 mg/kg/week (less than the
recommended dosage) to 30 mg/kg/week by intravenous infusion for 2 weeks at
each dose level.
Study 1 Part 2 was a 168-week, open-label study assessing
the efficacy and safety of VYONDYS 53 at a dose of 30 mg/kg/week in the 12
patients enrolled in Part 1, plus 13 additional treatment-naive patients with
DMD amenable to exon 53 skipping. At study entry (either in Part 1 or Part 2),
patients had a median age of 8 years and were on a stable dose of
corticosteroids for at least 6 months. Efficacy was assessed based on change
from baseline in the dystrophin protein level (measured as % of the dystrophin
level in healthy subjects, i.e., % of normal) at Week 48 of Part 2. Muscle
biopsies were obtained at baseline prior to treatment and at Week 48 of Part 2
in all VYONDYS 53-treated patients (n=25) and were analyzed for dystrophin
protein level by Western blot. Mean dystrophin levels increased from 0.10% (SD
0.07) of normal at baseline to 1.02% (SD 1.03) of normal by Week 48 of Study 1
Part 2, with a mean change in dystrophin of 0.92% (SD 1.01) of normal levels
(p<0.001); the median change from baseline was 0.88%.
Individual patient dystrophin levels from Study 1 are
shown in Table 2.
Table 2: Dystrophin Expression by Individual Patient
From Study 1
Patient Number |
Western Blot % Normal Dystrophin |
Patient number |
Western Blot % Normal Dystrophin |
Baseline |
Part 2 Week 48 |
Change from baseline |
Baseline |
Part 2 Week 48 |
Change from baseline |
1 |
0.08 |
0.09 |
0.01 |
14 |
0.22 |
0.28 |
0.06 |
2 |
0.11 |
0.11 |
0.01 |
15 |
0.14 |
0.21 |
0.07 |
3 |
0.21 |
0.22 |
0.01 |
16 |
0.05 |
0.42 |
0.37 |
4 |
0.05 |
0.12 |
0.08 |
17 |
0.07 |
1.03 |
0.97 |
5 |
0.03 |
0.12 |
0.09 |
18 |
0.02 |
1.57 |
1.55 |
6 |
0.06 |
0.14 |
0.09 |
19 |
0.12 |
1.17 |
1.05 |
7 |
0.12 |
0.37 |
0.25 |
20 |
0.03 |
1.72 |
1.69 |
8 |
0.11 |
1.06 |
0.95 |
21 |
0.11 |
1.77 |
1.66 |
9 |
0.06 |
0.54 |
0.48 |
22 |
0.31 |
4.30 |
3.99 |
10 |
0.05 |
0.97 |
0.92 |
23 |
0.11 |
0.36 |
0.25 |
11 |
0.06 |
1.55 |
1.49 |
24 |
0.03 |
0.91 |
0.88 |
12 |
0.07 |
1.91 |
1.84 |
25 |
0.07 |
1.29 |
1.22 |
13 |
0.10 |
3.25 |
3.15 |
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