Discovery of Highly Potent Human Glutaminyl Cyclase Inhibitors as Anti-Alzheimers Agents By the Combination of Pharmacophore-based and Structure-based Design

Abstract

본 박사 학위 논문은 알츠하이머병 (AD) 치료제 표석분자로 glutaminyl cyclase (QC) 기전의 신약 후보물질 도출을 위해 선행 선도 물질로부터 약리작용단 기반 및 효소구조 기반 디자인을 통해 구조활성연구를 통한 신약후보물질 최적화 연구이다. QC 효소는 아밀로이드 베타 (AB)로부터 아미노 펩티다아제에 의해 절단되어 생성되는 3번 및 11번 워치의 노출된 glutamate를 pyro-glutamate로 고리화하여 pE-AB form을 형성한다. 이 pE-AB form AB에 비해 빠른 속도로 독성용집체를 생성하며, 효소분해에 안정하여 AD 질환의 주요 발생인자로 확인되었다. 이런 이유로 OC 억제제에 의해 AB pyro form의 형성을 억제하는 것이 근원적 AD 치료 접근 방법으로 제안되어왔다. 선행 연구에서보고 된 Probiodrug 선도물질로부터 새로운 pharmacophore D를 추가 하 고, conformational blocker를 도입해 bioactive conformation을 갖도록 디자인한 새로운 scaffold에 대한 구조 활성 연구를 수행하다. 합성된 화합물들은 human QC에 대한 저해력 및 세포독성을 검색하였고,이 중 IC50 값이 10 nM 미만이고 세포독성이 없는 저해제를 선별하여 acute model에서의 효능실험, HERG, PAMPA 등의 실험을 수행 하여, 다음 단계로 진입할 수있는 후보물질을 도출 하였다. 본 연구 내용은 알츠하이머 치료제 후보물질로 우수한 신규 glutaminyl cyclase 저해제를 도출하여 향후 신약후보물질로의 개발 기반을 마련하였고, 또한 의약화학분야의 최상위 학술지 게재 한 바 약학박사 학위논문으로서 충분한 가치가 있다고 인정된다.

Alzheimers disease (AD) is a devastating neurodegenerative and progressive brain disorder in which the death of brain cells causes massive memory loss and cognitive dysfunction. The pathology of AD is complex and has not been fully understood. Among the proposed molecular mechanisms involved in AD, the amyloid hypothesis states that the accumulation of neurotoxic amyloid-β (Aβ) oligomers in the brain is the key molecular event in AD pathogenesis. This accumulation has been recognized as the most promising target for directed therapies. The pyroglutamate form of Aβ (AβN3pE) , a posttranslational product of N-truncated Aβ peptides, comprises a substantial proportion of Aβ peptides. In comparison to ordinary Aβ, AβpE3 species are shown to be aggregation-prone, more hydrophobic, more soluble, highly toxic and stable to degradation. Many studies also report that AβN3pE is found upstream of the amyloid cascade, contributing to the early stages of AD pathogenesis. Glutaminyl cyclase (QC), belonging to the family of metal-dependent aminoacyltransferases, catalyzes the conversion of the N-truncated Aβ peptide into the pyroglutamate peptide AβN3pE-40/42. The inhibition of glutaminyl cyclase (QC) may provide a promising strategy for the treatment of early Alzheimers disease (AD) by reducing the amount of the toxic pyroform of β-amyloid (AβN3pE) in the brains of AD patients. In this work, we identified potent QC inhibitors with subnanomolar IC50 values that were up to 290-fold higher than that of PQ912, which is currently being tested in Phase II clinical trials. Among the tested compounds, the cyclopentylmethyl derivative (214) exhibited the most potent in vitro activity (IC50 = 0.1 nM), while benzimidazole (227) showed the most promising in vivoefficacy, selectivity and druggable profile. 227 significantly reduced the concentration of pyroform Aβ and total Aβ in the brain of an AD animal model and improved the alternation behavior of mice during Y-maze tests. The crystal structure of human QC (hQC) in complex with 214 indicated tight binding at the active site, supporting that the specific inhibition of QC results in potent in vitro and in vivo activity. Considering the recent clinical success of donanemab, which targets AβN3pE, small molecule-based QC inhibitors may also provide potential therapeutic options for early-stage AD treatment.