An Open-Label Extension Study to Evaluate the Long-term Safety and Efficacy of BMN 351 in Participants With Duchenne Muscular Dystrophy

An Open-Label Extension Study to Evaluate the Long-term Safety and Efficacy of Weekly Intravenous Infusions of BMN 351 in Participants With Duchenne Muscular Dystrophy Amenable to Exon 51 Skipping

This open-label extension study aims to evaluate the long-term safety and tolerability of weekly BMN 351 infusions, as well as to assess the effect of BMN 351 on physical function, in participants with DMD who participated in the 351-201 study.

This Phase 2, multi-center, open-label extension study is designed to assess the long-term safety, tolerability, and functional efficacy of weekly intravenous doses of BMN 351 administered to participants with Duchenne muscular dystrophy (DMD) amenable to exon 51 skipping in the Phase 1/2 study, 351-201. Up to 18 participants ages 4 through 23 at baseline will enroll in the trial after completing 351-201.

The first visit for this study is the same as the final visit of 351-201. To be eligible for this study, potential participants must satisfy the eligibility criteria described in the protocol.

Inclusion Criteria:

• Participants must have completed 351-201 without permanent discontinuation of the investigational medicinal product (IMP) or withdrawal from the study

• Currently receiving treatment with oral corticosteroids, on a stable dose regimen during 351-201, and must remain on a consistent dose regimen throughout 351-202 or 351-203 except for modifications to accommodate changes in weight

  • Transition to the equivalent dose of vamorolone is permitted in 351-202 where approved in participating countries.

• Willing and able to adhere to the study visit schedule and other protocol requirements

• Willing to use contraception (sexually mature males) throughout the study and for 90 days after the final dose, if sexually active

  • Contraceptive use by males should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

• Willing and able to provide written assent (if required by local regulations or the IRB/IEC) after the nature of the study has been explained and prior to performance of any research-related procedure

• Willing and able to provide written, signed informed consent as parent or guardian after the nature of the study has been explained and prior to performance of any research-related procedure

Exclusion Criteria:

• Have known coagulation disorder

• Are taking any prohibited medications

  • any approved exon skipping therapy within 12 weeks prior to baseline or with any gene therapy for the treatment of DMD at any time
  • anti-coagulants, anti-thrombotics, or anti-platelet agents
  • immunosuppressants