Antibody-Drug Conjugate Targeting c-Kit for the Treatment of Small Cell Lung Cancer

Abstract

Lung cancer is the leading cause of cancer-related deaths. Small cell lung cancer (SCLC) accounts for 15–25% of all lung cancers. It exhibits a rapid doubling time and a high degree of invasiveness. Additionally, overexpression of c-Kit occurs in 70% of SCLC patients. In this study, we evaluated an antibody-drug conjugate (ADC) that targets c-Kit, which is a potential therapeutic agent for SCLC. First, we generated and characterized 4C9, a fully human antibody that targets c-Kit and specifically binds to SCLC cells expressing c-Kit with a binding affinity of KD = 5.5 × 10−9 M. Then, we developed an ADC using DM1, a microtubule inhibitor, as a payload. 4C9-DM1 efficiently induced apoptosis in SCLC with an IC50 ranging from 158 pM to 4 nM. An in vivo assay using a xenograft mouse model revealed a tumor growth inhibition (TGI) rate of 45% (3 mg/kg) and 59% (5 mg/kg) for 4C9-DM1 alone. Combination treatment with 4C9-DM1 plus carboplatin/etoposide or lurbinectedin resulted in a TGI rate greater than 90% compared with the vehicle control. Taken together, these results indicate that 4C9-DM1 is a potential therapeutic agent for SCLC treatment.

A Novel Antibody-Drug Conjugate Targeting Nectin-2 Suppresses Ovarian Cancer Progression in Mouse Xenograft Models

“…The conjugation of DM1 to c12G1 increased the absorbance at 252 nm ( Figure 4 B). The drug-to-antibody ratio (DAR) was determined as described previously [ 32 ] and found to be approximately 5.07. Since the target-binding affinity of ADC can be reduced by a conformational change via conjugation of the N-hydroxysuccinimide ester of the smcc linker with the primary amines of lysine in the antibody, we compared the binding affinity of 12G1 antibody and 12G1 ADC.…”

“…The c12G1 was subcloned into the pCHO 1.0 vector (Thermo Fisher Scientific, Waltham, MA, USA) and the recombinant plasmids were transiently transfected into CHO-S cells (Thermo Fisher Scientific) using OptiPRO™ SFM and FreeStyle™ MAX Reagent (both from Thermo Fisher Scientific), according to the manufacturer’s instructions. The antibody was purified using Protein A Sepharose and SP Sepharose columns (Invitrogen, Waltham, MA, USA), as described previously [ 32 ].…”

“…The ADCs were further analyzed using SDS-PAGE and ultraviolet spectrometry. Analysis of the DAR ratio was performed as previously described [ 32 ].…”

A fully human anti-c-Kit monoclonal antibody 2G4 inhibits proliferation and degranulation of human mast cells

“…Previous studies have demonstrated that 2G4 antibody, a fully human antibody, could inhibit the activation of SCF/c-Kit signaling in various cancer cell lines [ 34 , 35 ]. In addition, another anti-c-Kit antibody 4C9 significantly reduced the expression of c-Kit [ 36 ]. Both 2G4 and 4C9 antibodies could bind to human c-Kit with high binding affinity ( K D of 2G4 = 2.83 × 10 −12 M and K D of 4C9 = 5.58 × 10 −9 M) [ 34 , 36 ].…”

“…In addition, another anti-c-Kit antibody 4C9 significantly reduced the expression of c-Kit [ 36 ]. Both 2G4 and 4C9 antibodies could bind to human c-Kit with high binding affinity ( K D of 2G4 = 2.83 × 10 −12 M and K D of 4C9 = 5.58 × 10 −9 M) [ 34 , 36 ]. In this study, we investigated whether 2G4 and 4C9 could inhibit the proliferation and degranulation in LAD2, a human mast cell line.…”