CMV infection
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The US Food and Drug Administration (FDA) has granted breakthrough therapy designation to maribavir (SHP620) as a treatment for cytomegalovirus (CMV) infection and disease in transplant recipients who are resistant or refractory to prior therapy.
Maribavir, an antiviral therapy that belongs to a class of drugs called benzimidazole ribosides, is being evaluated in patients who have CMV infection after undergoing hematopoietic stem cell transplant or solid organ transplant.
The drug inhibits the CMV UL97 protein kinase and is thought to affect several critical processes in CMV replication, including viral DNA synthesis, viral gene expression, encapsidation, and egress of mature capsids from the nucleus.
The FDA granted maribavir breakthrough designation based on data from two phase 2 studies. For one of these studies (NCT00223925), data are not yet available.
The other study (NCT01611974) was presented at IDWeek 2016. This study included 120 patients ages 12 and older with CMV infection (≥1000 DNA copies/mL of blood plasma) that was resistant or refractory to (val)ganciclovir or foscarnet.
Forty-seven of the patients had received a hematopoietic stem cell transplant, and 73 had a solid organ transplant.
The patients were randomized to 1 of 3 twice-daily oral doses of maribavir—400 mg, 800 mg, or 1200 mg—for up to 24 weeks of treatment.
The study’s primary efficacy endpoint was the proportion of patients with confirmed undetectable plasma CMV DNA within 6 weeks of treatment. Sixty-seven percent (80/120) of patients met this endpoint. This included 70% (n=28) of patients in the 400 mg group, 63% (n=25) in the 800 mg group, and 67% (n=27) in the 1200 mg group.
CMV infection recurred in 30 patients, including 7 in the 400 mg group, 11 in the 800 mg group, and 12 in the 1200 mg group.
The incidence of treatment-emergent adverse events (AEs) was 78% (n=93) overall, 78% (n=31) in the 400 mg group, 80% (n=32) in the 800 mg group, and 75% (n=30) in the 1200 mg group.
Twenty-seven percent of patients died due to any AE, 1 of which (multi-organ failure) was considered possibly related to maribavir.
Forty-one patients (34%) discontinued treatment with maribavir due to an AE, including 17 patients who discontinued due to CMV infection.
Dysgeusia was the most common treatment-emergent AE and led to treatment discontinuation in 1 patient. Dysgeusia occurred in 65% (n=78) of all patients, including 60% (n=24) in the 400 mg group, 63% (n=25) in the 800 mg group, and 73% (n=29) in the 1200 mg group.
About breakthrough designation
The FDA’s breakthrough designation is intended to expedite the development and review of new treatments for serious or life-threatening conditions.
The designation entitles the company developing a therapy to more intensive FDA guidance on an efficient and accelerated development program, as well as eligibility for other actions to expedite FDA review, such as rolling submission and priority review.
To earn breakthrough designation, a treatment must show encouraging early clinical results demonstrating substantial improvement over available therapies with regard to a clinically significant endpoint, or it must fulfill an unmet need.
