Phase Ib study: APL-1202 (APL) in combination with Bacillus Calmette-Guerin (BCG) in recurrent non-muscle invasive bladder cancer (NMIBC).

e17039 Background: APL is a selective human methionine aminopeptidases II (MetAP2) inhibitor. In preclinical studies, APL has demonstrated both anti-angiogenic and anti-tumor activities as well as a potential synergistic effect with BCG or PD-1. A. This phase 1b study assesses the tolerability and pharmacokinetics (PK) characteristics of oral APL and intravesical BCG combination in HR NMIBC pts. Methods: Pts who had received a prior induction course of BCG within 12 weeks (wks) of enrollment and were scheduled to receive either maintenance or another induction course of BCG were given 750 mg/day APL (2x125 mg tablet, TID) for 12 wks. The tolerability and PK of APL was evaluated one wk prior to first BCG instillation and during combination use with BCG. AEs were evaluated to assess safety and tolerability. Wilcoxon matched-pair signed-rank test was used for PK analysis. Results: Six pts (4M, 2F) with a median age of 72.5 yrs (range 58-81 yrs) were enrolled; 4 pts had grade 3 Ta and 2 pts had Tis. Four and 2 pts received induction and maintenance course of BCG, respectively. Six AEs of grade 1 or 2 were reported by 3 pts, and they were respiratory and head congestion, acid reflux, rash, bronchitis, nausea, and cystitis. None of these AEs were judged to be related to APL. Five pts completed the study and 1 pt dropped out due to a grade 1 cystitis after receiving 4 wks of APL and 2 doses of BCG. The PK results suggested similar PK characteristics (plasma AUCtau, Cmax and t1/2, and urinary excreted faction Ae%). Conclusions: APL was well tolerated when given for 12 wks to NMIBC pts who also received induction or maintenance BCG. Further study of APL in combination with BCG is warranted. Clinical trial information: NCT03672240.

MapB Protein is the Essential Methionine Aminopeptidase in Mycobacterium tuberculosis

M. tuberculosis (Mtb), which causes tuberculosis disease, continues to be a major global health threat. Correct identification of valid drug targets is important for the development of novel therapeutics that would shorten the current 6–9 month treatment regimen and target resistant bacteria. Methionine aminopeptidases (MetAP), which remove the N-terminal methionine from newly synthesized proteins, are essential in all life forms (eukaryotes and prokaryotes). The MetAPs contribute to the cotranslational control of proteins as they determine their half life (N-terminal end rule) and facilitate further modifications such as acetylation and others. Mtb (and M. bovis) possess two MetAP isoforms, MetAP1a and MetAP1c, encoded by the mapA and mapB genes, respectively. Conflicting evidence was reported in the literature on which of the two variants is essential. To resolve this question, we performed a targeted genetic deletion of each of these two genes. We show that a deletion mutant of mapA is viable with only a weak growth defect. In contrast, we provide two lines of genetic evidence that mapB is indispensable. Furthermore, construction of double-deletion mutants as well as the introduction of point mutations into mapB resulting in proteins with partial activity showed partial, but not full, redundancy between mapB and mapA. We propose that it is MetAP1c (mapB) that is essentially required for mycobacteria and discuss potential reasons for its vitality.

Discovery of natural product ovalicin sensitive type 1 methionine aminopeptidases: molecular and structural basis

Natural product ovalicin and its synthetic derivative TNP-470 have been extensively studied for their antiangiogenic property, and the later reached phase 3 clinical trials. They covalently modify the conserved histidine in Type 2 methionine aminopeptidases (MetAPs) at nanomolar concentrations. Even though a similar mechanism is possible in Type 1 human MetAP, it is inhibited only at millimolar concentration. In this study, we have discovered two Type 1 wild-type MetAPs (Streptococcus pneumoniae and Enterococcus faecalis) that are inhibited at low micromolar to nanomolar concentrations and established the molecular mechanism. F309 in the active site of Type 1 human MetAP (HsMetAP1b) seems to be the key to the resistance, while newly identified ovalicin sensitive Type 1 MetAPs have a methionine or isoleucine at this position. Type 2 human MetAP (HsMetAP2) also has isoleucine (I338) in the analogous position. Ovalicin inhibited F309M and F309I mutants of human MetAP1b at low micromolar concentration. Molecular dynamics simulations suggest that ovalicin is not stably placed in the active site of wild-type MetAP1b before the covalent modification. In the case of F309M mutant and human Type 2 MetAP, molecule spends more time in the active site providing time for covalent modification.