Distinct mechanistic activity profile of pralatrexate in comparison to other antifolates in in vitro and in vivo models of human cancers.
OBJECTIVE
This study evaluated mechanistic differences of pralatrexate, methotrexate, and pemetrexed.


METHODS
Inhibition of dihydrofolate reductase (DHFR) was quantified using recombinant human DHFR. Cellular uptake and folylpolyglutamate synthetase (FPGS) activity were determined using radiolabeled pralatrexate, methotrexate, and pemetrexed in NCI-H460 non-small cell lung cancer (NSCLC) cells. The tumor growth inhibition (TGI) was assessed using MV522 and NCI-H460 human NSCLC xenografts.


RESULTS
Apparent K ( i ) values for DHFR inhibition were 45, 26, and >200 nM for pralatrexate, methotrexate, and pemetrexed, respectively. A significantly greater percentage of radiolabeled pralatrexate entered the cells and was polyglutamylatated relative to methotrexate or pemetrexed. In vivo, pralatrexate showed superior anti-tumor activity in both NSCLC models, with more effective dose-dependent TGI in the more rapidly growing NCI-H460 xenografts.


CONCLUSIONS
Pralatrexate demonstrated a distinct mechanistic and anti-tumor activity profile relative to methotrexate and pemetrexed. Pralatrexate exhibited enhanced cellular uptake and increased polyglutamylation, which correlated with increased TGI in NSCLC xenograft models.
Izbicka
E
E
CTRC IDD, San Antonio, TX, USA.
Diaz
A
A
Streeper
R
R
Wick
M
M
Campos
D
D
Steffen
R
R
Saunders
M
M
D000630:Aminopterin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D005971:Glutamates / Q000494:pharmacology; D006147:Guanine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008727:Methotrexate / Q000494:pharmacology; D009369:Neoplasms / Q000188:drug therapy*; D000068437:Pemetrexed; D011099:Polyglutamic Acid / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
C418863:10-propargyl-10-deazaaminopterin; D005493:Folic Acid Antagonists; D005971:Glutamates; D000068437:Pemetrexed; D011099:Polyglutamic Acid; D006147:Guanine; D013762:Tetrahydrofolate Dehydrogenase; D000630:Aminopterin; D008727:Methotrexate