Tengonermin

The therapeutic index of cytokines in cancer therapy can be increased by targeting strategies based on protein engineering with peptides containing the CNGRC (NGR) motif, a ligand that recognizes CD13-positive tumor vessels. We show here that the targeting domain of recombinant CNGRC-cytokine fusion proteins, such as NGR-TNF (a CNGRC-tumor necrosis factor-α (TNF) conjugate used in clinical studies) and NGR-EMAP-II, undergoes various post-translational modification and degradation reactions that lead to the formation of markedly heterogeneous products. These modifications include N-terminal cysteine acetylation or the formation of various asparagine degradation products, the latter owing to intramolecular interactions of the cysteine α-amino group with asparagine and/or its succinimide derivative. Blocking the cysteine α-amino group with a serine (SCNGRC) reduced both post-translational and degradation reactions. Furthermore, the serine residue reduced the asparagine deamidation rate to isoaspartate (another degradation product) and improved the affinity of NGR for CD13. Accordingly, genetic engineering of NGR-TNF with the N-terminal serine produced a more stable and homogeneous drug (called S-NGR-TNF) with improved antitumor activity in tumor-bearing mice, either when used alone or in combination with chemotherapy. In conclusion, the targeting domain of NGR-cytokine conjugates can undergo various untoward modification and degradation reactions, which can be markedly reduced by fusing a serine to the N-terminus. The SCNGRC peptide may represent a ligand for cytokine delivery to tumors more robust than conventional CNGRC. The S-NGR-TNF conjugate (more stable, homogeneous, and active than NGR-TNF) could be rapidly developed for clinical trials.

Patients with primary central nervous system lymphoma (PCNSL) are treated with high-dose methotrexate-based chemotherapy, which requires hospitalization and extensive expertise to manage related toxicity. The use of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) could overcome these difficulties, but blood-brain barrier (BBB) penetration of related drugs is poor. Tumor necrosis factor-α coupled with NGR (NGR-hTNF), a peptide targeting CD13+ vessels, induces endothelial permeabilization and improves tumor access of cytostatics. We tested the hypothesis that NGR-hTNF can break the BBB, thereby improving penetration and activity of R-CHOP in patients with relapsed/refractory PCNSL (NCT03536039). Patients received six R-CHOP21 courses, alone at the first course and preceded by NGR-hTNF (0.8 μg/m2) afterward. This trial included 2 phases: an “explorative phase” addressing the effect of NGR-hTNF on drug pharmacokinetic parameters and on vessel permeability, assessed by dynamic contrast-enhanced magnetic resonance imaging and 99mTc-diethylene-triamine-pentacetic acid–single-photon emission computed tomography, and the expression of CD13 on tumor tissue; and an “expansion phase” with overall response rate as the primary end point, in which the 2-stage Simon Minimax design was used. At the first stage, if ≥4 responses were observed among 12 patients, the study accrual would have continued (sample size, 28). Herein, we report results of the explorative phase and the first-stage analysis (n = 12). CD13 was expressed in tumor vessels of all cases. NGR-hTNF selectively increased vascular permeability in tumoral/peritumoral areas, without interfering with drug plasma/cerebrospinal fluid concentrations. The NGR-hTNF/R-CHOP combination was well tolerated: there were only 2 serious adverse events, and grade 4 toxicity was almost exclusively hematological, which were resolved without dose reductions or interruptions. NGR-hTNF/R-CHOP was active, with 9 confirmed responses (75%; 95% confidence interval, 51-99), 8 of which were complete. In conclusion, NGR-hTNF/R-CHOP was safe in these heavily pretreated patients. NGR-hTNF enhanced vascular permeability specifically in tumoral/peritumoral areas, which resulted in fast and sustained responses.