The U.S. Food and Drug Administration (FDA) granted approval to Turalio (pexidartinib) capsules for the treatment of adult patients with symptomatic tenosynovial giant cell tumor (TGCT) associated with severe morbidity or functional limitations and not responsive to improvement with surgery.
Tenosynovial giant cell tumor is a non-malignant tumor involving the joint synovium, bursae, and tendon sheath. These rare tumors are sometimes referred to as giant cell tumor of the tendon sheath (GCT-TS) and/or pigmented villonodular synovitis (PVNS).TGCT can appear at any joint. Several studies have examined which joints are most affected and there is yet to be a consensus. One of the more comprehensive studies was by Mastboom et al (2017) involving 4,503 cases of TGCT and they found that the majority of tumors were located locally in the digits (68%) followed by those described as localized-extremity (knee, wrist, elbow, hip, etc; 23%), and the remaining 9% were diffuse-type tumors. Within those localized-extremity and diffuse TGCTs, the most dominant joint affected was the knee (48% of localized-extremity TGCTs and 64% of diffuse TGCTs, respectively).
Even though TGCTs are not malignant, they can grow and cause damage to nearby tissue resulting in pain and movement limitations.
In most cases, surgery is used to remove the tumor, but the exact type of surgery will be dependent on the size/position of tumor and which joint is involved. For diffuse or localized-extremity tumors, surgery may or may not be an option and other treatment options are in development that may be more applicable. Currently, no systemic treatment is approved for this rare disease.
The approval of Turalio was based on the results of a multi-center international clinical trial of 120 patients, 59 of whom received placebo. The primary efficacy endpoint was the overall response rate (ORR) analyzed after 25 weeks of treatment. The clinical trial demonstrated a statistically significant improvement in ORR in patients who received Turalio, with an ORR of 38%, compared to no responses in patients who received placebo. The complete response rate was 15% and the partial response rate was 23%.
The prescribing information for Turalio includes a Boxed Warning to advise health care professionals and patients about the risk of serious and potentially fatal liver injury. Health care professionals should monitor liver tests prior to beginning treatment and at specified intervals during treatment. If liver tests become abnormal, Turalio may need to be withheld, the dose reduced, or permanently discontinued, depending on the severity of the liver injury. Turalio is available only through the Turalio Risk Evaluation and Mitigation Strategy (REMS) Program.
Common side effects for patients taking Turalio were increased lactate dehydrogenase (proteins that helps produce energy in the body), increased aspartate aminotransferase (enzymes that are mostly in the liver but also in muscles), loss of hair color, increased alanine aminotransferase (enzymes that are primarily in the liver and kidney) and increased cholesterol. Additional side effects included neutropenia (low level of white blood cells that help the immune system defend against disease and infection), increased alkaline phosphatase (enzymes that are mostly in the cells of bone and the liver), decreased lymphocytes (white blood cells that help the immune system defend against disease and infection), eye edema (swelling around the eyes), decreased hemoglobin (protein in red blood cells that carry oxygen), rash, dysgeusia (altered sense of taste) and decreased phosphate (electrolytes that help with energy).
The FDA granted this application Breakthrough Therapy designation and Priority Review designation. Turalio also received Orphan Drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases. The FDA granted the approval of Turalio to Daiichi Sankyo.
For more information, visit the Tenosynovial Giant Cell Tumor (TGCT) Learning Center on this topic.