Dendrimer-enhanced (DEP) SN38 (DEP irinotecan) in patients (pts) with advanced solid tumors: A phase 1/2 trial.
Authors: Liu Jia (Jenny) , Minchom Anna Rachel , Greystoke Alastair , Evans T.R. Jeffry , Sarker Debashis , Joshua Anthony M. , Morton Cienne , Aktas Burak Y , Cosman Rasha , Chwialkowska Dominika , Paull Jeremy , Main Nicola Jane , Jean-Francois Bernadette Marie , Le Meur Julia , Edmondson Stephanie Ruth , Cook Natalie 
Published: July 2024

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Background: Dendrimer nanoparticles enable prolonged cytotoxic drug targeting to tumors. DEP SN38 is a water-soluble version of SN38, the active metabolite of irinotecan, attached to a dendrimer, so avoiding usual metabolic pathways of conventional irinotecan (c-IRI). This phase 1/2 (P1/2) trial evaluated safety, tolerability and efficacy of DEP SN38 in pts with advanced solid tumors, including colorectal (CRC), platinum-resistant high-grade serous ovarian (HGSOC) and breast (BC). Methods: Pts who had exhausted standard therapy were enrolled in dose assessment (P1)/dose expansion (P2) cohorts of DEP SN38 given IV 3-weekly (Q3W) or Q2W alone or in combination with 5-fluorouracil & leucovorin (5FU/LV combo). Efficacy was evaluated by RECIST 1.1 and serum tumor markers. (EudraCT 2019-001318-40). Results: 114 pts were enrolled. The Q3W Recommended Dose (RD) was 12.5 mg/m2 SN38 with dose limiting toxicity (DLT) in 1/7 pts (grade (G) 4 neutropenia > 7d). The Q2W RD was 12.5 mg/m2 for SN38 alone or with 5FU/LV. DEP SN38 was well-tolerated for all dose regimens with mostly mild/moderate (G1/2) treatment-related adverse events (TRAEs) & no new events compared with c-IRI. TRAEs in ≥ 10% pts included neutropenia, thrombocytopenia, anemia, fatigue, nausea, vomiting, diarrhea, constipation and alopecia. Of734 DEP SN38 cycles only 1 event of G3 diarrhea (0.9% pts) and no cholinergic symptoms have been observed, contrasting with c-IRI (~20% & 47% pts respectively). G3 nausea (1.8% pts) and vomiting (0.9% pts) occurred less frequently than with c-IRI (both ~10% pts). Febrile neutropenia was the DLT at 15 mg/m2 Q2W monotherapy (2/6 pts), with neutropenia otherwise essentially uneventful and managed with G-CSF. 38 CRC pts received DEP SN38 monotherapy (31 evaluable) and 17 received the 5FU/LV combo (14 evaluable). CRC pts had a mean 4 prior lines with 97% receiving ≥ 1 c-IRI containing line. The disease control rate (DCR) in monotherapy was 48% (stable disease (SD) up to 72 wks). The 5FU/LV combo cohort DCR was 85.7%, the objective response rate (ORR) was 14.3%, with disease control observed for at least 35 wks. Several CRC pts continue combo treatment. 23 HGSOC pts with a mean of 6 prior lines received DEP SN38 monotherapy (18 evaluable). The DCR for Q2W was 100% with 33.3% ORR, and 72% DCR for all HGSOC pts. 3 pts have PRs for at least 36 wks; with 1 pt achieving complete tumor & ascites resolution. Reduced CA-125 of up to 98% was observed in 75% pts. Several HGSOC pts continue DEP SN38 treatment. 8 BC pts with a mean of 7 prior lines received DEP SN38 monotherapy Q3W (5 evaluable). The DCR was 100% with SD up to 72 wks. Conclusions: DEP SN38 shows promising clinical utility with encouraging antitumor activity including prolonged disease control & durable PRs in heavily pre-treated CRC, HGSOC & BC pts. DEP SN38 is well-tolerated with significantly fewer severe gastrointestinal TRAEs compared to c-IRI, & warrants further clinical assessment. Clinical trial information: 2019-001318-40 .