The Food and Drug Administration has approved avapritinib (Ayvakit), a targeted therapy for adults with gastrointestinal (GI) stromal tumors that are unresectable or metastatic and have a specific mutation of platelet-derived growth factor receptor alpha (PDGFRA) exon 18, including PDGFRA D842V (a particular location on the exon 18 gene). These mutations do not respond to standard therapies for GI stromal tumors.

Approval was based on a multicenter, single-arm, open-label trial of 43 patients with this form of GI stromal tumor, a subgroup of which (38) had the PDGFRA D842V mutation. The trial measured overall response rate (the proportion of patients whose tumor was destroyed or significantly reduced by the drug), which was 84% (7% complete response, 77% partial response) for those with the PDGFRA exon 18 mutation and 89% (8% complete response, 82% partial response) for those with the PDGFRA D842V mutation. The response to avapritinib lasted six months or longer for 61% of those with PDGFRA exon 18 mutations.

Serious adverse effects of avapritinib include intracranial hemorrhage, central nervous system effects (cognitive impairment, dizziness, sleep disorders, mood disorders, speech disorders, and hallucinations), and embryo-fetal toxicity. Common adverse effects include edema, nausea, fatigue/asthenia, cognitive impairment, vomiting, decreased appetite, diarrhea, hair color changes, increased lacrimation, abdominal pain, constipation, rash, and dizziness.

Nurses should confirm that patients have been tested for this genetic variation prior to receiving avapritinib. Men and women should use effective birth control while receiving avapritinib because of the risk of embryo-fetal harm. Patients who experience central nervous system effects shouldn't drive or operate hazardous machinery. In patients who experience serious adverse effects, the avapritinib dose might need to be stopped temporarily, discontinued permanently, or restarted at a different dose depending on the degree of severity.

For complete prescribing information for avapritinib, go to http://www.accessdata.fda.gov/drugsatfda_docs/label/2020/212608s000lbl.pdf.