Long-Term Safety & Efficacy of Apitegromab in Patients With SMA Who Completed Previous Trials of Apitegromab

Inclusion Criteria:

• Patients have completed the Phase 2 TOPAZ (Study SRK-015-002) trial or the Phase 3SAPPHIRE (Study SRK-015-003) trial. (For TOPAZ, completed is defined as completionof Visit EC14 in Extension Period C or participating in TOPAZ at the time the trialis ended. For SAPPHIRE, completed is defined as completion of Visit 14 orparticipating in SAPPHIRE at the time the trial is ended)

• Estimated life expectancy >2 years from the Baseline Visit (Day 1)

• Able to receive study drug infusions and provide blood samples through the use of aperipheral IV or a long-term IV access device that the patient has placed forreasons independent from the trial

• Able to adhere to the requirements of the protocol, including travel to the trialsite and completing all trial procedures and trial visits

• Females of childbearing potential must have a negative pregnancy test at theBaseline Visit and agree to use at least 1 highly effective method of contraceptionthroughout the trial and for 20 weeks after the last dose of apitegromab

Exclusion Criteria:

• Patient permanently discontinued study treatment during the feeder trial (i.e.,TOPAZ or SAPPHIRE)

• Nutritional status that was not stable over the past 6 months and is not anticipatedto be stable throughout the trial or medical necessity for a gastric/nasogastricfeeding tube, where the majority of feeds are given by this route, as assessed bythe Investigator

• Patient is currently enrolled in any investigational drug trial other than TOPAZ orSAPPHIRE

• Prior history of severe hypersensitivity reaction or intolerance to SMN-targetedtherapies

• Prior history of severe hypersensitivity reaction or intolerance to apitegromab

• Use of chronic daytime noninvasive ventilatory support for >16 hours daily in the 2weeks before dosing, or anticipated to regularly receive such daytime ventilatorsupport chronically throughout the trial

• Any acute or comorbid condition interfering with the well-being of the patient atthe patient's last visit in TOPAZ or SAPPHIRE, (including active systemic infection,the need for acute treatment, or inpatient observation due to any reason). Afterresolution of the condition, the patient can be enrolled in the trial if they meetall the other eligibility criteria.

• Pregnant or breastfeeding

• Any other condition or clinically significant laboratory result or ECG value that,in the opinion of the Investigator, may compromise safety or compliance, wouldpreclude the patient from successful completion of the trial, or interfere with theinterpretation of the results