Incidence and management of mTOR inhibitor-associated pneumonitis in patients with metastatic renal cell carcinoma

The administration of mammalian target of rapamycin (mTOR) inhibitors can give rise to a potentially life-threatening adverse event, often referred to as 'non-infectious pneumonitis' (NIP), which is characterized by non-infectious, non-malignant, and non-specific inflammatory infiltrates. Patients usually present with cough and/or dyspnoea. We provide a brief description of the mechanism of action of mTOR inhibitors and their overall safety in patients with metastatic renal cell carcinoma (mRCC) and review the literature on mTOR inhibitor-associated NIP in patients with solid tumours. The review was used to derive questions on the diagnosis, management, and monitoring of mRCC patients with NIP, and to develop a decision tree for use in routine clinical practise. A key recommendation was the subdivision of grade 2 NIP into grades 2a and 2b, where grade 2a is closer to grade 1 and grade 2b to grade 3. This subdivision is important because it takes into account the nature and severity of clinical symptoms potentially related to NIP, either the onset of new symptoms or the worsening of existing symptoms, and thus determines the type and frequency of follow-up. It also helps to identify a subgroup of patients in whom treatment, if effective, may be continued without dose adjustment.

Phase I study for ridaforolimus, an oral mTOR inhibitor, in Japanese patients with advanced solid tumors

Purpose

Ridaforolimus is a non-prodrug mTOR inhibitor. The safety, pharmacokinetics (PK), and antitumor activity of oral ridaforolimus were assessed in Japanese patients with refractory solid tumors.

Methods

Ridaforolimus (20 or 40 mg) was administered as a single dose on Day 1, followed by once daily dosing five times a week for a 3-week cycle beginning on Day 8. Full PK sampling was performed on Days 1 and 26.

Results

Thirteen patients (7 at 20 mg and 6 at 40 mg) were enrolled. The median treatment duration was 82 days. The most common drug-related adverse events were stomatitis, hypertriglyceridemia, and proteinuria. Two patients had dose-limiting toxicities (grade 3 stomatitis at 20 mg, and grade 3 anorexia and vomiting at 40 mg). Four patients had grade 1 interstitial pneumonitis. Ridaforolimus in the whole blood was rapidly absorbed and slowly eliminated with a half-life of approximately 56–58 h after a single dose. Two patients (with non-small cell lung cancer and angiosarcoma, respectively) achieved a partial response, and five patients (one with thymic cancer and four with soft tissue sarcomas) had a stable disease for ≥16 weeks.

Conclusions

Ridaforolimus was well tolerated up to a dose of 40 mg in Japanese patients. Preliminary evidence of antitumor activity was observed for patients with solid tumors. Further investigation at this dose is warranted.