Proof of concept for monoclonal antibody therapy in a cellular model of acquired long QT syndrome type 3

Figures

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  Figure 1.. Effect of six different monoclonal KCNQ1 antibodies on slow component of the delayed rectifier K+ current (IKs). Represented are IKs step (A) and tail (B) current densities as a function of the test potential comparing control cells (n = 16, mean cell capacitance 17.2 ± 2.2 pF) and cells treated with 30 µg/mL monoclonal antibodies: mAB-1 (n = 15, 16.7 ± 1.1 pF), mAB-2 (n = 12, 18.2 ± 1.9 pF), mAB-3 (n = 8, 18.4 ± 2.5 pF), mAB-4 (n = 8, 20.8 ± 3.4 pF), mAB-5 (n = 8, 17.7 ± 1.9 pF), and mAB-6 (n = 5, 26.0 ± 6.3 pF).

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  Figure 2.. Effect of mAB-1 monoclonal antibody on slow component of the delayed rectifier K+ current (IKs). Representative IKs traces recorded in Chinese hamster ovary (CHO) cells under control condition (A; cell capacitance, 13.7 pF) and in the presence of 30 µg/mL mAB-1 (B; 13.6 pF). C and D: IKs step and tail current densities as a function of the test potential comparing control cells (n = 16) and cells treated with mAB-1 (n = 15). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. E: voltage-dependent activation of IKs. In the presence of mAB-1, IKs were activated at more negative potentials compared with control cells (P < 0.0001), without manifest effect on the slope factor k [control, half-maximal activation potential (V1/2) = 23.6 ± 1.3 mV, k = 16.9 ± 1.2 mV; mAB-1, V1/2 = 14.6 ± 0.9 mV, k = 17.5 ± 1.0 mV]. F: voltage-dependent deactivation of IKs. mAB-1 led to a leftward shift of the voltage-dependence of deactivation (P < 0.0001), whereas not affecting the slope factor k (control, V1/2 = 20.0 ± 1.4 mV, k = 15.9 ± 1.4 mV; mAB-1, V1/2 = 8.7 ± 1.1 mV, k = 14.2 ± 1.1 mV).

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  Figure 3.. Effect of mAB-1 monoclonal antibody on human iPSC-cardiomyocytes (hiPSC-CMCs). A: representative action potential traces recorded in hiPSC-CMCs under control condition and in the presence of 30 µg/mL mAB-1. B: bars represent mean action potential duration at 90% repolarization (APD90) of control cells (n = 15) and cardiomyocytes treated with 5 µg/mL (n = 4), 10 µg/mL (n = 10), 20 µg/mL (n = 11), 30 µg/mL (n = 14), and 60 µg/mL (n = 14) mAB-1. **P < 0.01, ***P < 0.001, ****P < 0.0001. C: concentration-response curve for the absolute APD90 reduction effect at five different concentrations of mAB-1. A sigmoidal curve fit to the data determined an EC50 of 5.7 µg/mL (R2 = 0.9967).

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  Figure 4.. Effect of mAB-1 monoclonal antibody on human iPSC-cardiomyocytes (hiPSC-CMCs) in the context of pharmacological LQTS type 3. A: representative action potentials recorded in hiPSC-CMCs challenged with sea anemone toxin 2 (ATX-II) leading to early afterdepolarizations (EADs) and arrhythmic beating. B: representative action potentials recorded in hiPSC-CMCs treated with 30 µg/mL mAB-1 and challenged with ATX-II. Bars represent the incidence of EADs and arrhythmic beating (C) and mean APD90 (D) of hiPSC-CMCs challenged with ATX-II (n = 16) ± 30 µg/mL mAB-1 (n = 14). ****P < 0.0001.