Two cases of pneumonitis induced by targeted therapy

Interstitial pneumonitis is a rare drug adverse effect. We report two cases of cobimetinib-induced and vemurafenib-induced reversible interstitial pneumonitis. Two patients presenting a BRAF-mutated metastatic melanoma were treated with cobimetinib and vemurafenib. After 3 months, they developed severe feverish dyspnea. Thoracic imaging showed a pattern of organizing pneumonia in one case and a pattern of hypersensitivity pneumonitis in the other case. Infectious and cardiogenic causes were eliminated. An improvement was noted after discontinuation of cobimetinib, vemurafenib, and introducing steroids. Treatment was switched to dabrafenib (a BRAF inhibitor) with no recurrence of drug pneumonitis. To the best of our knowledge, it appears that cases of targeted-therapy-induced pneumonitis are predominantly an MEK-inhibitor effect. We, therefore, propose a management strategy of discontinuing targeted therapy, introducing steroid treatment and switching to dabrafenib.