The CHMP recommended granting conditional marketing authorization for avapritinib (Ayvakit, Blueprint Medicines) for use in adults with unresectable or metastatic gastrointestinal stromal tumors (GIST) harboring a platelet-derived growth factor receptor alpha (PDGFRA) exon 18 mutation, including PDGFRA D842V mutations. About 6%-10% of GIST tumors harbor this mutation, and avapritinib is a selective and potent inhibitor of KIT and PDGFRA mutant kinases.
The CHMP also adopted a positive opinion for acalabrutinib (Calquence, AstraZeneca) for the treatment of chronic lymphocytic leukemia (CLL) as monotherapy in patients who are treatment-naive or have received at least one prior therapy.
The CHMP opinion on both drugs will be reviewed by the European Commission, which has the authority to grant marketing authorization for medicinal products in the EU.
Detailed recommendations for the use of both drugs will be provided in the summary of product characteristics, which will be published in the European public assessment report and made available in all official EU languages after the products receive marketing authorization by the European Commission.
First targeted therapy for mutation
If approved by the European Commission, avapritinib would be the first treatment in the EU indicated for patients with PDGFRA D842V-mutant GIST.
Avapritinib was approved by the US Food and Drug Administration (FDA) earlier this year for the aforementioned indication. The FDA approval was based on findings from the phase 1 NAVIGATOR trial, which included 43 patients with GIST harboring a PDGFRA exon 18 mutation, including 38 patients with the most common mutation, PDGFRA D842V.
For patients harboring a PDGFRA exon 18 mutation, the overall response rate (ORR) was 84%, with 7% having a complete response and 77% having a partial response. Patients with the PDGFRA D842V mutation achieved an ORR of 89%, with 8% having a complete response and 82% having a partial response.
“GIST harboring a PDGFRA exon 18 mutation do not respond to standard therapies ... Today’s approval provides patients with the first drug specifically approved for GIST harboring this mutation,” said Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence, in a statement at the time of approval.
The most common side effects (≥ 20% of patients) observed in patients taking avapritinib include nausea, fatigue, anemia, periorbital edema, face edema, hyperbilirubinemia, diarrhea, vomiting, peripheral edema, increased lacrimation, decreased appetite, and memory impairment. There may also be a risk of intracranial hemorrhage, in which case the dose should be reduced or the drug should be discontinued.
In the EU, conditional marketing authorization is granted to a medicinal product that fulfills an unmet medical need when the benefit to public health of immediate availability outweighs the risk inherent in the fact that additional data are still required, the CHMP notes on its website.
Avapritinib had received an orphan medicine designation during development, which the EMA will review to determine if the designation can be maintained.
New treatment for CLL
Acalabrutinib is already approved in the United States, Canada, and Australia for the treatment of CLL and small lymphocytic lymphoma. The product was approved at the same time by all three regulatory authorities last year. In the United States, acalabrutinib had previously been approved for use in mantle cell lymphoma.
The CHMP’s positive opinion of acalabrutinib is based on results from two phase 3 trials, ELEVATE TN and ASCEND.
In the ASCEND trial, acalabrutinib was compared with investigator’s choice of idelalisib or bendamustine with rituximab. The trial, which involved 310 patients with relapsed/refractory CLL, showed that acalabrutinib improved progression-free survival (PFS).
At a median follow-up of 16.1 months, the median PFS was not reached with acalabrutinib and was 16.5 months with investigator’s choice of therapy (P < .0001).
The most commonly reported adverse events seen with acalabrutinib were respiratory tract infections, headache, bruising, contusion, diarrhea, nausea, rash, musculoskeletal pain, fatigue, decreased hemoglobin, and decreased platelets.
In the ELEVATE TN trial, acalabrutinib was given alone or combined with obinutuzumab and compared to chlorambucil plus obinutuzumab in patients with previously untreated CLL. There were 535 patients randomized to receive acalabrutinib alone (n = 179), acalabrutinib plus obinutuzumab (n = 179), and chlorambucil plus obinutuzumab (n = 177).
At a median follow-up of 28 months, the median PFS was not reached with acalabrutinib alone or with acalabrutinib plus obinutuzumab, but the median PFS was 22.6 months in the chlorambucil-obinutuzumab arm (P < .0001 for both comparisons).
The most common adverse events in the acalabrutinib arms were headache, diarrhea, neutropenia, and nausea.
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