Duchenne muscular dystrophy (DMD) is a severe, progressive muscle-degenerating disease and the most common form of muscular dystrophy. Its inheritance pattern is X-linked recessive and is caused by mutations on the gene that produces dystrophin, a protein essential for muscle health and mobility. GlobalData’s upcoming report, Duchenne Muscular Dystrophy: Opportunity Assessment and Forecast to 2030 indicates 23 DMD-targeting therapeutics currently being developed in the US and Japan. Figure 1 summaries all pipeline products in Phase I, II, and III of drug development.

Among pipeline agents, the majority are in Phase II of drug development. GlobalData anticipates that eight late-stage candidates (Phase IIb–III) could make it to market within the next 10 years. Their great diversity in mechanism of action indicates the important unmet need and potential of the DMD space. Late-stage candidates include gene therapies, a cell therapy, a monoclonal antibody, and small molecules. Key opinion leaders (KOLs) interviewed by GlobalData were enthusiastic about these products, expecting them to be efficacious and have better safety and tolerability profiles in comparison to steroids.

Two gene therapies are currently being investigated in the US, namely, Pfizer ’s fordadistrogene movaparvovec (NCT04281485) and Sarepta’s delandistrogene moxeparvovec (NCT05096221), of which the first is also being tested in Japan. Both are intravenously (IV) administered products in Phase III of clinical trials and are designed to deliver a micro-dystrophin encoding gene to muscle tissue. The dystrophin gene is the largest known encoding human gene that is too large to fit on an adeno-associated viral (AAV) vector. The micro-dystrophin gene is an abbreviated version with less than one-fifth the size of the normal gene and able to fit in AAV vectors utilized by Pfizer and Sarepta, while still providing functional protein.

KOLs interviewed by GlobalData were hopeful that, should they make it to market, these products could replace marketed exon-skipping therapies, considering their potential to treat most, if not all, DMD patient segments. However, Pfizer’s recent announcement of the exclusion of patients with certain mutations from its trial due to side effects has led to safety concerns. Thus, approval for all ages may be hindered by a need for extensive, long-term safety data.

CAP-1002 (NCT03406780) is a cell therapy in Phase IIb developed by Capricor , which according to the company modifies the immune system and has the potential to encourage cellular regeneration. It is a first-in-class IV drug mainly tested on non-ambulatory patients, the DMD patient segment with the highest unmet need to date. KOLs anticipate that CAP-1002 could be co-administered with other DMD-targeting treatments, aiming to support cardiac function of patients in latter stages of the disease.

FibroGen’s pamrevlumab is a monoclonal antibody (mAb) with antifibrotic action aiming to inhibit connective tissue growth factor. It is an IV product in Phase III of clinical trials for both ambulatory (NCT04632940) and non-ambulatory patients (NCT04371666). Despite pamrevlumab’s interesting approach, KOLs believed that more data on its safety is required and that its uptake could be mediocre if the drug does not prove to be game-changing in terms of efficacy during clinical studies.

Finally, small molecules in late stages of development are PTC Therapeutics’ Translarna (NCT01247207, NCT03179631, NCT04336826, NCT02369731), Italfarmaco ’s givinostat (NCT03373968), Taiho ’s pizuglanstat (NCT04587908), and Santhera’s vamorolone (NCT03439670). These are oral products aiming to tackle DMD. Each has a different mechanism of action and all four of them have displayed encouraging results. Translarna has so far managed to receive approval in the EU for ambulatory patients; however, it has been rejected three times by the FDA due to lack of adequate data on its efficacy, a fact that PTC is trying to address with its current four ongoing trials.

Of these drugs, KOLs have been particularly enthusiastic about vamorolone, a synthetic steroid, as it could be administered instead of traditional steroids but with a considerably better tolerability profile. A major question that has yet to be determined is which of these drugs could eventually be administered as a monotherapy and could therefore bypass the adverse effects that come along with steroid use.

Current DMD treatment options are still limited. For decades, the gold standard for management of DMD has been the delay of disease progression through the use of steroids, namely prednisone, as they decrease inflammation and decelerate deterioration of muscle function and force. However, serious side effects that come with long-term steroid use include stunted growth in adolescents, bone fragility, and weight gain, which have led to pursuit of safer options. Recently approved steroid Emflaza (deflazacort) and exon-skipping therapies provide additional treatment options. Exon-skipping therapies enhance the therapeutic outcome by increasing dystrophin levels but also have their own limitations as they are typically co-administered with steroids and only target patient segments with specific mutations.

DMD is a space with great untapped potential, a fact underlined by the limited available products and the highly diverse candidates under development. The current pipeline in the US and Japan holds numerous promising candidates with the majority in Phase II of clinical trials. Current late-stage pipeline products could overcome existing unmet needs and considerably improve treatment of DMD. Should these candidates make it to market, they could substantially change the competitive landscape of the DMD space and potentially replace current therapies in the treatment algorithm. Taking into consideration the existing unmet needs of DMD patients, these drugs are expected to have a strong market uptake, either as monotherapies or as add-on medications.

Cell & Gene Therapy Coverage on Clinical Trials Arena supported by Cytiva.

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