Background: NGR-hTNF exploits the peptide asparagine-glycine-arginine (NGR) for selectively targeting tumour necrosis factor (TNF) to CD13-overexpressing tumour vessels. Maximum-tolerated dose (MTD) of NGR-hTNF was previously established at 45 μg m(-2) as 1-h infusion, with dose-limiting toxicity being grade 3 infusion-related reactions. We explored further dose escalation by slowing infusion rate (2-h) and using premedication (paracetamol).
Methods: Four patients entered each of 12 dose levels (n=48; 60-325 μg m(-2)). Pharmacokinetics, soluble TNF receptors (sTNF-R1/sTNF-R2), and volume transfer constant (K(trans)) by dynamic imaging (dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)) were assessed pre- and post-treatment.
Results: Common related toxicity included grade 1/2 chills (58%). Maximum-tolerated dose was not reached. Both C(max) (P<0.0001) and area under the plasma concentration-time curve (P=0.0001) increased proportionally with dose. Post-treatment levels of sTNF-R2 peaked significantly higher than sTNF-R1 (P<0.0001). Changes in sTNF-Rs, however, did not differ across dose levels, suggesting a plateau effect in shedding kinetics. As best response, 12/41 evaluable patients (29%) had stable disease. By DCE-MRI, 28/37 assessed patients (76%) had reduced post-treatment K(trans) values (P<0.0001), which inversely correlated with NGR-hTNF C(max) (P=0.03) and baseline K(trans) values (P<0.0001). Lower sTNF-R2 levels and greater K(trans) decreases after first cycle were associated with improved survival.
Conclusion: asparagine-glycine-arginine-hTNF can be safely escalated at doses higher than MTD and induces low receptors shedding and early antivascular effects.