CASE REPORT: A male smoker aged 51 years with denovo metastatic NSCLC was treated with first-line chemoimmunotherapy. After 4 cycles, an EML4-ALK fusion was identified. At time of disease progression, alectinib 600mg BID was started after an 8-week washout period. Within 2 weeks, he developed a pruritic rash covering 90% of his BSA that required hospitalization and IV steroids. Biopsy confirmed a spongiotic and interface dermatitis with eosinophils consistent with a drug eruption. Rash was reported as an adverse event in the ALEX trial in 17% of patients treated with front-line alectinib but grade 3 rash was reported in only 1%.
A literature search demonstrated successful case reports of alectinib de-sensitization and thus a de-sensitization protocol was devised. Alectinib was started at 150mg daily and increased to 300mg BID over 2 weeks. His rash worsened resulting in a drug hold, treatment with oral prednisone, and a dose reduction to 300mg daily. The dose was increased to 300mg/450mg over 1 week when he developed painful mouth erosions. This resulted in a second dose hold and reduction to 300mg BID. After 2 weeks, alectinib was discontinued due to worsening rash with a plan to switch to an alternate ALK TKI, a strategy which has been successfully reported in the literature. Lorlatinib 100mg was recommended given phase 2 data demonstrating very low rates of rash (5% grade 1-2 and < 1% grade 3). While he did experience a facial rash within 2 weeks, a dose hold or reduction was not required. Nonetheless, lorlatinib was discontinued after 4 weeks due to other intolerable side effects and hypertriglyceridemia
DISCUSSION: Pembrolizumab has a terminal half-life of 22 days with steady state reached at 16 weeks with every 3-week dosing. It is therefore possible that prior exposure to pembrolizumab exacerbated the cutaneous toxicity of alectinib in this case. Multiple studies have shown that combining immunotherapy with alectinib leads to substantially more adverse events.
CONCLUSION: In patients with alectinib hypersensitivity, a de-sensitization protocol can be attempted. If hypersensitivity recurs, switching to an alternate ALK TKI is warranted. However, if immunotherapy has been previously administered without time for adequate washout, no TKI therapy may be tolerable.