EACR25-1342

Biological Basis for the Development of CPL410005 as an Antibody-Drug Conjugate

F. Mituła1, D. Popiel1, T. Kornatowski1, M. Mroczkiewicz2, W. Pyra1, J. Hucz-Kalitowska1, O. Abramczyk1, M. Marczak1, M. Wieczorek3, J. Pieczykolan1
1Celon Pharma S.A., Preclinical Development Department, Kazuń Nowy, Poland
2Celon Pharma S.A., Medicinal Chemistry Department, Kazuń Nowy, Poland
3Celon Pharma S.A., Pre- and Clinical Development Department, Kazuń Nowy, Poland
Introduction:

CPL410005 is a potent UBA1 inhibitor with strong anti-cancer activity in vitro. However, its systemic toxicity and poor tumor selectivity limit its therapeutic potential as a standalone small-molecule drug. To overcome these limitations, this study explores the conjugation of CPL410005 to an anti-HER2 antibody to enhance tumor specificity and reduce off-target effects. Targeting the Ubiquitin-Proteasome System (UPS) with Antibody-Drug Conjugate (ADC) for directed UBA1 inhibition represents a promising strategy for cancer therapy.

Material and method:

CPL410005 cytotoxicity was assessed across a broad panel of cancer cell lines. Its pharmacokinetic properties, including solubility, metabolic stability, and hepatotoxicity, were evaluated in vitro. To improve tumor-specific targeting, CPL410005 was conjugated to an anti-HER2 antibody via a selectively cleavable linker. ADCs were characterized in vitro for stability, HER2 binding affinity (SPR), and cytotoxic effects in HER2-positive and HER2-negative cell lines.

Result and discussion:

CPL410005 exhibited potent in vitro cytotoxicity on a panel of 130 cell lines, with IC50 values of 15.3 nM in U937 and 22.7 nM in HCT116 cell lines. However, systemic administration in xenograft models resulted in dose-limiting toxicity at 10 mg/kg. ADC conjugation significantly improved tumor-specific uptake, with conjugation yields above 85%, as confirmed by RP-HPLC. HER2-ADC conjugates retained high HER2 binding affinity (KD = 1.2 nM) and displayed selective cytotoxicity in HER2-overexpressing SK-OV-3 and SK-BR-3 cells, with IC50 values of 1.8 nM and 2.5 nM, respectively. No significant cytotoxicity was observed in HER2-negative HEK293 cells at concentrations up to 1 µM. Pharmacokinetic studies showed prolonged plasma half-life (t1/2 = 18.2 h) compared to free CPL410005 (t1/2 = 2.9 h), while linker cleavage-dependent drug release ensured selective cytotoxicity in target cells.

Conclusion:

CPL410005’s potent UBA1 inhibition utilized in the form of ADC technology enhances tumor selectivity and reduces systemic toxicity. These findings support further preclinical development of HER2-targeted UBA1 inhibitors as a novel therapeutic strategy for HER2-positive cancers. Project co-financed by NCBR, POIR.01.02.00-00-0009/17