Table 1.

PSMA expression and cytotoxicity data

ZJ24 BindingNo. of PSMA molecules per cellaIC50, nmol/L
Cell linePhenotypeBmaxKd, nmol/LPSMA ADCMMAEControl ADCDocetaxelPaclitaxel
MDAPCa2bAndrogen dependent PSMA positive319,000 ± 19,30046.5 ± 5.9159,5000.018 ± 0.0080.363 ± 0.07882.1 ± 6.31.20 ± 0.276.17 ± 1.58
LNCaPAndrogen dependent PSMA positive251,900 ± 9,30039.4 ± 2.9125,9500.019 ± 0.0120.502 ± 0.09378.5 ± 6.61.55 ± 0.185.90 ± 1.13
C4-2Androgen independent PSMA positive204,900 ± 4,60035.5 ± 0.8102,4500.011 ± 0.0140.298 ± 0.07557.8 ± 1.91.75 ± 0.1012.6 ± 0.58
CWR22rv1Androgen independent weakly PSMA positive26,500 ± 50035.6 ± 3.913,2500.804 ± 0.1671.44 ± 0.1998.8 ± 5.43.55 ± 0.6617.1 ± 1.1
PC3Androgen independent PSMA negativeno specific bindingN/AN/A83.4 ± 6.30.970 ± 0.17496.2 ± 2.36.98 ± 0.8941.8 ± 5.6
DU145Androgen independent PSMA negativeno specific bindingN/AN/A99.1 ± 5.40.911 ± 0.120156.0 ± 5.47.47 ± 0.4846.0 ± 7.8
PC3PIRESpuroPC3 transfection controlno specific bindingN/AN/A31.8 ± 3.70.775 ± 0.13829.9 ± 3.7NDND
PC3wtPSMAPC3 transfected with wild-type PSMA75,800 ± 1,1008.20 ± 1.4637,9000.022 ± 0.0110.667 ± 0.15038.5 ± 3.8NDND
PC3L5APC3 transfected with internalization mutant PSMA20,700 ± 4005.06 ± 2.6310,3508.17 ± 2.70.737 ± 0.17532.4 ± 2.7NDND
PC3N638APC3 transfected with glycosylation mutant PSMAno specific bindingN/AN/A12.4 ± 2.20.594 ± 0.11048.2 ± 2.2NDND

NOTE: Data represent the mean ± SD of triplicate determinations. Bmax = molecules of ZJ24 per cell. PSMA mAb did not exhibit measurable cytotoxicity at concentrations ranging up to 1,000 nmol/L.

Abbreviations: N/A, not applicable; ND, not done.

  • aExpression levels of dimeric PSMA are estimated to be 1-half of the Bmax observed for ZJ24, because PSMA is a symmetric dimer that contains 2 identical binding sites for ZJ24.