According to Cure Today, the U.S. FDA granted Orphan Drug designation to MB-106, a novel CAR-T cell therapy designed to treat Waldenström macroglobulinemia (WM). In the United States, Orphan Drug designation is granted to drugs or biologics intended to treat, diagnose, or prevent rare diseases or life-threatening conditions. Rare diseases are those affecting fewer than 200,000 Americans. As a benefit, drug developers – in this case, Mustang Bio – receive incentives such as fee waivers, tax credits, increased regulatory assistance, and seven years of market exclusivity upon approval. Given that no current CAR-T cell therapies exist for WM, MB-106 has the potential to change the treatment landscape for this rare cancer.

About MB-106

In a PDF from Mustang Bio, the company describes MB-106 as:

a fully human third-generation CD20 targeted CAR with both 4-1BB and CD28 costimulatory domains.

MB-106 is administered intravenously. At this time, Mustang Bio is evaluating MB-106 for a variety of oncologic indications, including B-cell non-Hodgkin’s lymphoma (B-cell NHL) in a clinical study. 

Prior studies regarding MB-106 have shown promising results from individuals with B-cell NHL, follicular lymphoma, and WM. Study findings showed that 94% of those within the trial responded to MB-106 treatment, with 78% achieving a complete response. This shows high efficaciousness in treatment. 

What is Waldenström Macroglobulinemia (WM)?

In many cases, individuals who develop Waldenström macroglobulinemia (WM), a rare lymphoma, start with a slow-progressing condition called monoclonal gammopathy of unknown/undetermined significance (MGUS). However, MGUS may progress into WM. Additionally, MYD88 gene mutations have been implicated in the development of this rare cancer. Waldenström macroglobulinemia begins in B lymphocytes, causing the accumulation of abnormal IgM. As cancerous cells crowd out healthy blood cells, the blood becomes hyperviscous. 

Men are 2x more likely to develop WM than women. Another risk factor is age, with the prevalence increasing with age. If symptoms of WM manifest, they can include:

• Anemia (low red blood cell count)
• Low platelet and white blood cell counts
• Easy bruising and bleeding
• Frequent infections
• Unintended weight loss
• Diarrhea
• Abdominal distention
• Raised pink or flesh-colored skin lesions
• Enlarged spleen lymph nodes
• Fatigue and general malaise/weakness
• Breathlessness 
• Frequent nose bleeds
• Blurred vision and/or vision loss
• Dizziness and headaches
• Difficulty concentrating