Dendrimer-Nanoparticle (DEP) Delivery of Topoisomerase I Inhibitor, SN38 (DEP-SN38): Safety, Tolerability, and Preliminary Efficacy Study in Patients With Advanced Solid Tumors

PURPOSE This early-phase study evaluated safety/tolerability, pharmacokinetics, and preliminary efficacy of dendrimer-nanoparticle delivery platform (DEP)-SN38, a polylysine-based nanoparticle conjugate of the irinotecan active metabolite, SN38. METHODS Adults with advanced solid tumors received DEP-SN38 intravenously once every 3 weeks (Q3W) or once every 2 weeks (Q2W) monotherapy, or Q2W combined with fluorouracil/leucovorin (FU/LV) to identify a recommended dose for each regimen. Primary end points were safety/tolerability. Secondary end points included efficacy (RECIST-v1.1) and pharmacokinetics. RESULTS Heavily pretreated patients (N = 114; median 4 previous therapies) received DEP-SN38 (8-15-mg/m 2 SN38), with 12.5 mg/m 2 recommended for all regimens. Most DEP-SN38–attributed treatment-related adverse events (TRAEs) were mild/moderate (89.7%), with neutropenia the key dose-limiting toxicity and the most common grade 3/4 TRAE (48% of grade 3/4 events). Severe GI TRAEs were rare (grade 3 diarrhea and vomiting [0.9% of patients each]; nausea [1.8%]). Cholinergic symptoms were not observed. Efficacy signals were observed across several tumor types, particularly Q2W regimens and in patients with platinum-resistant ovarian cancer (PROC) and colorectal cancer (CRC). Among evaluable patients, objective response rates for Q3W or Q2W monotherapy and Q2W DEP-SN38/FU/LV were 1.8%, 21.4% (PROC 42.9%), and 12.5% (CRC 14.3%), respectively; disease control rates were 56.4%, 71.4%, and 81.3%, respectively. Median progression-free survival (PFS, all treated) was 2.1, 6.0, and 4.2 months for Q3W, Q2W, and Q2W DEP-SN38/FU/LV, respectively. Patients achieving PFS for at least 6 months included seven PROC (Q2W monotherapy, n = 5; > 12 months, n = 3), 12 CRC (DEP-SN38/FU/LV, n = 6, including four patients for >12 months), one pancreatic (10.2 months), one non-small cell lung (8.4 months), and two with breast cancer (16.6 months, 6 months). CONCLUSION DEP-SN38 was clinically well tolerated with minimal severe GI TRAEs. Preliminary antitumor activity in heavily pretreated patients with cancer demonstrates the potential clinical utility of DEP-SN38 monotherapy and combination regimens.