Spinraza Nusinersen 2.4 mg/mL Injection, Solution — NDC 64406-058-01 (Billing 64406-0058-01)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action SPINRAZA is an antisense oligonucleotide (ASO) designed to treat SMA caused by mutations in chromosome 5q that lead to SMN protein deficiency. Using in vitro assays and studies in transgenic animal models of SMA, SPINRAZA was shown to increase exon 7 inclusion in SMN2 messenger ribonucleic acid (mRNA) transcripts and production of full-length SMN protein.

12.2Pharmacodynamics Autopsy samples from patients (n=3) had higher levels of SMN2 messenger ribonucleic acid (mRNA) containing exon 7 in the thoracic spinal cord compared to untreated SMA infants. Cardiac Electrophysiology Across the sham-controlled studies in 247 patients with spinal muscular atrophy who received either SPINRAZA Low Dose Regimen or sham-control, QTcF values > 500 ms and change from baseline values > 60 ms were observed in 4 (2.4%) patients receiving SPINRAZA. Compared to the sham-control, there was no increase in the incidence of cardiac adverse reactions associated with delayed ventricular repolarization in patients treated with SPINRAZA.

12.3Pharmacokinetics Absorption Intrathecal injection of SPINRAZA into the cerebrospinal fluid (CSF) allows nusinersen to be distributed from the CSF to the target central nervous system (CNS) tissues. Following intrathecal administration, trough plasma concentrations of nusinersen were relatively low, compared to the trough CSF concentration. Median plasma Tmax values ranged from 1.7 to 6.0 hours.

Mean plasma Cmax and AUC values increased approximately dose-proportionally up to a dose of 12 mg. Distribution Autopsy data from patients (n=3) showed that SPINRAZA administered intrathecally was distributed within the CNS and peripheral tissues, such as skeletal muscle, liver, and kidney. Elimination Metabolism Nusinersen is metabolized via exonuclease (3'- and 5')-mediated hydrolysis and is not a substrate for, or inhibitor or inducer of CYP450 enzymes.

Excretion The mean terminal elimination half-life is estimated to be 135 to 177 days in CSF, and 63 to 87 days in plasma. The primary route of elimination is likely by urinary excretion for nusinersen and its chain-shortened metabolites. At 24 hours, only 0.5% of the administered dose was recovered in the urine.

12.6Immunogenicity The observed incidence of anti-drug antibodies is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of anti-drug antibodies in the studies described below with the incidence of anti-drug antibodies in other studies, including those of SPINRAZA or of other nusinersen products. The immunogenic response to nusinersen in patients who received SPINRAZA Low Dose Regimen was evaluated in 367 patients with post-baseline plasma samples for anti-drug antibodies (ADAs).

Thirty eight patients (10%) developed treatment-emergent ADAs, of which 16 were transient and 22 were considered to be persistent. Persistent was defined as having one positive test followed by another one more than 100 days after the first positive test. In addition, “persistent” is also defined as having one or more positive samples and no sample more than 100 days after the first positive sample.

Transient was defined as having one or more positive results and not confirmed to be persistent. The immunogenic response to nusinersen in patients who received SPINRAZA High Dose Regimen was evaluated in 117 patients with post-baseline plasma samples for ADAs. Eleven patients (9%) developed treatment-emergent ADAs, of which 5 were transient and 6 were persistent.

There are insufficient data to evaluate an effect of ADAs on clinical response, adverse events, or the pharmacokinetic profile of nusinersen.

12.1Mechanism of Action SPINRAZA is an antisense oligonucleotide (ASO) designed to treat SMA caused by mutations in chromosome 5q that lead to SMN protein deficiency. Using in vitro assays and studies in transgenic animal models of SMA, SPINRAZA was shown to increase exon 7 inclusion in SMN2 messenger ribonucleic acid (mRNA) transcripts and production of full-length SMN protein.

12.3Pharmacokinetics Absorption Intrathecal injection of SPINRAZA into the cerebrospinal fluid (CSF) allows nusinersen to be distributed from the CSF to the target central nervous system (CNS) tissues. Following intrathecal administration, trough plasma concentrations of nusinersen were relatively low, compared to the trough CSF concentration. Median plasma Tmax values ranged from 1.7 to 6.0 hours.

Mean plasma Cmax and AUC values increased approximately dose-proportionally up to a dose of 12 mg. Distribution Autopsy data from patients (n=3) showed that SPINRAZA administered intrathecally was distributed within the CNS and peripheral tissues, such as skeletal muscle, liver, and kidney. Elimination Metabolism Nusinersen is metabolized via exonuclease (3'- and 5')-mediated hydrolysis and is not a substrate for, or inhibitor or inducer of CYP450 enzymes.

Excretion The mean terminal elimination half-life is estimated to be 135 to 177 days in CSF, and 63 to 87 days in plasma. The primary route of elimination is likely by urinary excretion for nusinersen and its chain-shortened metabolites. At 24 hours, only 0.5% of the administered dose was recovered in the urine.

12.2Pharmacodynamics Autopsy samples from patients (n=3) had higher levels of SMN2 messenger ribonucleic acid (mRNA) containing exon 7 in the thoracic spinal cord compared to untreated SMA infants. Cardiac Electrophysiology Across the sham-controlled studies in 247 patients with spinal muscular atrophy who received either SPINRAZA Low Dose Regimen or sham-control, QTcF values > 500 ms and change from baseline values > 60 ms were observed in 4 (2.4%) patients receiving SPINRAZA. Compared to the sham-control, there was no increase in the incidence of cardiac adverse reactions associated with delayed ventricular repolarization in patients treated with SPINRAZA.

14 CLINICAL STUDIES The efficacy of SPINRAZA Low Dose Regimen was demonstrated in two double-blind, sham-procedure controlled clinical trials in patients with symptomatic infantile-onset and later-onset SMA (Study 1 and Study 2) and was supported by open-label clinical trials conducted in patients with presymptomatic (Study 3) and symptomatic SMA [see Dosage and Administration ( 2.1 )] . The efficacy of SPINRAZA High Dose Regimen was demonstrated in a double-blind, randomized, external-controlled trial in patients with symptomatic infantile-onset and later-onset SMA (Study 4).

The overall findings from these trials support the effectiveness of SPINRAZA administered with either the Low Dose Regimen or the High Dose Regimen across the range of ages and severities in patients with SMA, and support the early initiation of treatment with SPINRAZA.

14.1Infantile-Onset SMA Study 1 (NCT02193074) was a multicenter, randomized, double-blind, sham-procedure controlled study in 121 symptomatic infants ≤ 7 months of age at the time of first dose, diagnosed with SMA (symptom onset before 6 months of age). Patients were randomized 2:1 to receive either SPINRAZA Low Dose Regimen or sham injection as a series of loading doses administered intrathecally followed by maintenance doses administered every 4 months. Patients in this study were deemed most likely to develop Type 1 SMA.

A planned interim efficacy analysis was conducted based on patients who died, withdrew, or completed at least 183 days of treatment. Of the 82 patients included in the interim analysis (52 patients in the SPINRAZA-treated group and 30 in the sham-control group), 44% were male, 87% were Caucasian, 2% were Black, and 4% were Asian. Age at first treatment ranged from 30 to 262 days (median 181).

Length of treatment ranged from 6 to 442 days (median 261 days). Baseline demographics were balanced between the SPINRAZA and control groups with the exception of age at first treatment (median age 175 vs. 206 days, respectively).

The SPINRAZA and control groups were balanced with respect to gestational age, birth weight, disease duration, and SMN2 copy number. Median disease duration was 14 weeks. There was some imbalance in age at symptom onset with 88% of subjects in the SPINRAZA group and 77% in the control group experiencing symptoms within the first 12 weeks of life.

The primary endpoint assessed at the time of interim analysis was the proportion of responders: patients with an improvement in motor milestones according to Section 2 of the Hammersmith Infant Neurologic Exam (HINE). This endpoint evaluates seven different areas of motor milestone development, with a maximum score between 2-4 points for each, depending on the milestone, and a total maximum score of 26. A treatment responder was defined as any patient with at least a 2-point increase (or maximal score of 4) in ability to kick (consistent with improvement by at least 2 milestones), or at least a 1-point increase in the motor milestones of head control, rolling, sitting, crawling, standing or walking (consistent with improvement by at least 1 milestone).

To be classified as a responder, patients needed to exhibit improvement in more categories of motor milestones than worsening. Of the 82 patients who were eligible for the interim analysis, a statistically significantly greater percentage of patients achieved the definition of a motor milestone responder in the SPINRAZA group (40%) compared to the sham-control group (0%). Results from the final analysis were consistent with those from the interim analysis ( Table 5 ).

Fifty-one percent of patients in the SPINRAZA group achieved the definition of a motor milestone responder compared to 0% of patients in the sham-control group. Figure 1 is a descriptive display of the distribution of net change from baseline in the total motor milestone score for Section 2 of the HINE for patients in the final efficacy set who did not die or withdraw from the study. The primary end… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis Administration of nusinersen (0, 5, 15, or 50 mg/kg) to male and female mice by subcutaneous injection, once every two weeks for 2 years, resulted in an increase in the incidence of vascular tumors (combined hemangioma and hemangiosarcoma) at the highest dose tested. Mutagenesis Nusinersen demonstrated no evidence of genotoxicity in in vitro (Ames and chromosomal aberration in CHO cells) and in vivo (mouse micronucleus) assays. Impairment of Fertility When nusinersen (0, 3, 10, or 25 mg/kg) was administered by subcutaneous injection to mice every other day prior to and during mating and continuing in females throughout organogenesis, no adverse effects on male or female fertility were observed.