Idelalisib in Combination With Rituximab or Bendamustine or Both in Patients With Relapsed/Refractory Chronic Lymphocytic Leukemia.

Phosphatidylinositol 3-kinase-delta (PI3Kδ) signaling is critical for proliferation, survival, homing, and tissue retention of malignant B cells. Idelalisib, a selective oral inhibitor of PI3Kδ, has shown considerable single-agent activity in patients with heavily pretreated chronic lymphocytic leukemia (CLL). This study evaluated the safety and clinical activity of idelalisib in combination with bendamustine (IB) or rituximab (IR) or both (IBR) in patients with relapsed or refractory (R/R) CLL. Idelalisib was given continuously at 100 or 150 mg twice daily in combination with rituximab (375 mg/m2 weekly × 8 doses), bendamustine (70 or 90 mg/m2, days 1 and 2 every 4 weeks × 6 cycles) or BR (rituximab, 375 mg/m2 every 4 weeks and bendamustine, 70 mg/m2, days 1 and 2 every 4 weeks × 6 cycles). The primary endpoint was safety; secondary endpoints included overall response rate (ORR), duration of response (DOR), and progression-free survival (PFS). Fifty-two patients (median age 64 years) with a median of 3 prior therapies were enrolled. ORR was 84.6% (89.5% IR group, 77.8% IB group, and 86.7% IBR group). The overall median PFS was 25.6 months, and median DOR was 26.6 months. The most common grade ≥3 adverse events (≥10% of patients) were pneumonia (19.2%), diarrhea (13.5%), and febrile neutropenia (17.3%). Idelalisib-based combination therapy with bendamustine and/or rituximab was highly active, resulting in durable tumor control in patients with heavily pretreated R/R CLL. However, its tolerability profile suggests that these regimens should be used cautiously in this patient population. ClinicalTrials.gov ID: NCT01088048.

Assessment of cellular proliferation in tumors by PET using 18F-ISO-1.

UNLABELLED: This first study in humans was designed to evaluate the safety and dosimetry of a cellular proliferative marker, N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2-(18)F-fluoroethoxy)-5-methylbenzamide ((18)F-ISO-1), and evaluate the feasibility of imaging tumor proliferation by PET in patients with newly diagnosed malignant neoplasms. METHODS: Patients with biopsy-proven lymphoma, breast cancer, or head and neck cancer underwent (18)F-ISO-1 PET. Tumor (18)F-ISO-1 uptake was assessed semiquantitatively by maximum standardized uptake value, ratios of tumor to normal tissue and tumor to muscle, and relative distribution volume ratio. The PET results were correlated with tumor Ki-67 and mitotic index, from in vitro assays of the tumor tissue. The biodistribution of (18)F-ISO-1 and human dosimetry were evaluated. RESULTS: Thirty patients with primary breast cancer (n = 13), head and neck cancer (n = 10), and lymphoma (n = 7) were evaluated. In the entire group, tumor maximum standardized uptake value and tumor-to-muscle ratio correlated significantly with Ki-67 (τ = 0.27, P = 0.04, and τ = 0.38, P = 0.003, respectively), but no significant correlation was observed between Ki-67 and tumor-to-normal-tissue ratio (τ = 0.07, P = 0.56) or distribution volume ratio (τ = 0.26, P = 0.14). On the basis of whole-body PET data, the gallbladder is the dose-limiting organ, with an average radiation dose of 0.091 mGy/MBq. The whole-body and effective doses were 0.012 mGy/MBq and 0.016 mSv/MBq, respectively. No adverse effects of (18)F-ISO-1 were encountered. CONCLUSION: The presence of a significant correlation between (18)F-ISO-1 and Ki-67 makes this agent promising for evaluation of the proliferative status of solid tumors. The relatively small absorbed doses to normal organs allow for the safe administration of up to 550 MBq, which is sufficient for PET imaging in clinical trials.