Abstract A97: Final phase 1/2a results evaluating the cyclodextrin-containing nanoparticle CRLX101 in patients with advanced solid tumor malignancies.
Authors: Yen Yun , Coerver Lori A. , Garmey Edward G. , Kalinoski D. Lynn , Koczywas Marianna , Neidhart James A. , Neidhart Jeffrey D. , Peterkin Joanna J. , Ramanathan Ramesh K. , Ryan John , Weiss Glen J. 
Published: June 2012

Introduction: Topoisomerase-1-inhibiting camptothecin (CPT) and derivatives such as irinotecan (CPT-11) and topotecan demonstrate clinical utility across multiple cancer types. Use of these agents remains limited by insufficient tumor exposure and high systemic toxicity. A novel cyclodextrin-containing polymer conjugate of CPT that self-assembles into nanoparticles, CRLX101 delivers sustained levels of active CPT into cancer cells while substantially reducing systemic exposure. In vitro and in vivo data suggest superior activity of CRLX101 in multiple tumor models. Efforts are made now to demonstrate the safety and efficacy of CRLX101 in human patients with advanced solid tumor malignancies.

Experimental Procedures: CRLX101 was administered intravenously over 1 hour every other week (EOW) to patients (pts.) with advanced and multiply pre-treated solid tumor malignancies. In phase 1, 24 pts. received CRLX101 at 5 escalating dose levels. Following identification of a maximum tolerated dose (MTD), a 38 patient phase 2a MTD-expansion cohort was enrolled at 3 clinical sites.

Summary of Data: As of a data cut-off of 6/1/11, 62 total pts. (31 F; 31 M) received CRLX101 at doses ranging from 6 mg/m2 to 18 mg/m2 of CPT equivalent per dose. In phase 1, 2 pts. (18 mg/m2) experienced dose limiting toxicity of CTCAE v3.0 grade (G)4 thrombocytopenia with one of these pts. additionally experiencing G4 neutropenia. An MTD/recommended phase 2 dose (RP2D) of CRLX101 was established at 15 mg/m2 EOW. Among 44 phase 1 or 2a pts. receiving the MTD/RP2D, most common grade 3/4 adverse events considered by investigators to be at least possibly related to study drug included neutropenia (9 events observed among 6 pts.) and lymphopenia (3 events observed among 2 pts.). Phase 2a pts. received CRLX101 for periods of time ranging from 1 day to approximately 13 months (mos.) with an average duration of 3.3 mos. Among 36 evaluable phase 2a pts. receiving the MTD, mean plasma Cmax and AUCall were 306 μg./L. and 27.1 mg./L.*hr. (polymer-unconjugated) and 8260 μg./L. and 300 mg./L.*hr. (polymer-conjugated), respectively. Mean urinary clearance of polymer-conjugated and free CPT over the 0–8 hr., 8–24 hr., and 24–48 hr. collection intervals post CRLX101 dosing were 0.0299, 0.0074, and 0.0062 L./hr. (polymer-conjugated) and 0.0888, 0.0898, and 0.1010 L./hr. (free CPT), respectively. Among all phase 2a pts., overall median progression-free survival (mPFS) was 3.7 mos., with mPFS of 4.4 mos. observed among 21 NSCLC pts. (4.8 mos. excluding 6/21 pts. with squamous cell histology). At time of data cut-off, 6 pts. (incl. 3 NSCLC pts.) remain on therapy. Notably, of the 21 NSCLC pts. in phase 2a (with an average of 3 prior regimens of chemotherapy), 66.7% (14/21) achieved stable disease (SD) ≥ 3 mos. and 14.3% (3/21) achieved SD ≥ 6 mos.

Conclusions: CRLX101 appears to be extremely well tolerated with an MTD/RP2D of 15 mg/m2 EOW. Pharmacokinetics are linear and suggest prolonged duration of CPT tumor exposure. Similarly, extended periods of stable disease observed across multiple tumor types are encouraging and merit further investigation. Patients are currently being enrolled into a multinational randomized clinical trial in 2nd/3rd line NSCLC and additional studies in renal cell cancer, small-cell lung cancer, ovarian cancer, and gastric cancer are being developed.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A97.