Abstract 2044: Chemotherapy induced neutropenia in rats following administration of eflapegrastim or pegfilgrastim on the same day at three different timepoints and at 24 hours post-chemotherapy

Abstract Background: Eflapegrastim is a long-acting G-CSF that is comprised of a G-CSF analog and a recombinant IgG4 Fc fragment conjugated at their N-termini via a short polyethylene glycol linker. Currently, G-CSF products are administered 24 hours after chemotherapy. We compared the duration of neutropenia (DN) after treatment with eflapegrastim and pegfilgrastim given on the same-day, at three different timepoints, and after 24 hours in chemotherapy-induced neutropenic rats. Method: Neutropenia was induced in rats via intraperitoneal administration of cyclophosphamide and docetaxel (TC) chemotherapy. Rats (5 animals per group) were assigned to dose groups of either vehicle or equivalent doses (based on human clinical doses) of pegfilgrastim (103.3 µg/kg) or eflapegrastim (61.8 µg/kg as G-CSF) on the same day as chemotherapy at 0, 2, and 5 hours or 24 hours after chemotherapy. The primary endpoint was the difference in DN after TC treatment and administration of eflapegrastim or pegfilgrastim at the specified timepoints. Results: In the vehicle group, the TC regimen induced neutropenia in all animals with an ANC nadir occurring on approximately Day 4 and a mean DN of nearly 7 days. The mean DN values for treatment with eflapegrastim on the same day, at 0, 2, and 5 hours, and after 24 hours were similar and the mean DN values for eflapegrastim were significantly lower than for pegfilgrastim at all dosing timepoints (Table). Time after Chemotherapy(hours)Mean Duration of Neutropenia (days)Difference (95% CI)Eflapegrastim Time vs 24 hoursDifference (95% CI)EflapegrastimPegfilgrastim00.62.2-1.6 (-3.067, -0.133)0.4 (-0.08, 1.28)20.21.8-1.6 (-2.84, -0.36)0 (-0.19, 0.59)50.01.2-1.2 (-1.20, -1.20)-0.2 (0, 0)240.21.8-1.6 (-2.84, -0.36)NA Conclusions: The DN for same-day treatment with eflapegrastim at 0, 2, and 5 hours was similar to that of the treatment after 24-hours. However, the mean DN values were significantly lower for eflapegrastim than pegfilgrastim at all time points. Further exploration of the potential advantage of same-day dosing with eflapegrastim in patients undergoing chemotherapy is warranted. Citation Format: Yu-Yon Kim, Eunjung Kim, Hyesun Han, Seungjae Baek, Shanta Chawla, Prasad Kolli, Gajanan Bhat, Francois Lebel. Chemotherapy induced neutropenia in rats following administration of eflapegrastim or pegfilgrastim on the same day at three different timepoints and at 24 hours post-chemotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2044.