Mechanistic study of the spiroindolones: a new class of antimalarials

Spirofused Tetrahydroisoquinoline-Oxindole Hybrids (Spiroquindolones) as Potential Multitarget Antimalarial Agents: Preliminary Hit Optimization and Efficacy Evaluation in Mice

Previous studies suggest that 3',5'-dihydro-2'H-spiro[indoline-3,1'-isoquinolin]-2-ones (DSIIQs [spiroquindolones]) are multitarget antiplasmodial agents that combine the actions of spiroindolone and naphthylisoquinoline antimalarial agents. In this study, 12 analogues of compound (±)-5 (moxiquindole), the prototypical spiroquindolone, were synthesized and tested for antiplasmodial activity. Compound (±)-11 (a mixture of compounds 11a and 11b), the most potent analogue, displayed low-nanomolar activity against P. falciparum chloroquine-sensitive 3D7 strain (50% inhibitory concentration [IC₅₀] for 3D7 = 21 ± 02 nM) and was active against all major erythrocytic stages of the parasite life cycle (ring, trophozoite, and schizont); it also inhibited hemoglobin metabolism and caused extensive vacuolation in parasites. In drug-resistant parasites, compound (±)-11 exhibited potent activity (IC₅₀ for Dd2 = 58.34 ± 2.04 nM) against the P. falciparum multidrug-resistant Dd2 strain, and both compounds (±)-5 and (±)-11 displayed significant cross-resistance against the P. falciparum ATP4 mutant parasite Dd2 SJ733 but not against the Dd2 KAE609 strain. In mice, both compounds (±)-5 and (±)-11 displayed dose-dependent reduction of parasitemia with suppressive 50% effective dose (ED₅₀) values of 0.44 and 0.11 mg/kg of body weight, respectively. The compounds were also found to be curative in vivo and are thus worthy of further investigation.

Spirocyclic Scaffolds in Medicinal Chemistry

Spirocyclic scaffolds are incorporated in various approved drugs and drug candidates. The increasing interest in less planar bioactive compounds has given rise to the development of synthetic methodologies for the preparation of spirocyclic scaffolds. In this Perspective, we summarize the diverse synthetic routes to obtain spirocyclic systems. The impact of spirocycles on potency and selectivity, including the aspect of stereochemistry, is discussed. Furthermore, we examine the changes in physicochemical properties as well as in in vitro and in vivo ADME using selected studies that compare spirocyclic compounds to their nonspirocyclic counterparts. In conclusion, the value of spirocyclic scaffolds in medicinal chemistry is discussed.

The early preclinical and clinical development of cipargamin (KAE609), a novel antimalarial compound

BACKGROUND

Cipargamin (KAE609) is a novel spiroindolone class drug for the treatment of malaria, currently undergoing phase 2 clinical development. This review provides an overview and interpretation of the pre-clinical and clinical data of this possible next-generation antimalarial drug published to date.

METHODS

We systematically searched the literature for studies on the preclinical and clinical development of cipargamin. PubMed and Google Scholar databases were searched using the terms 'cipargamin', 'KAE609' or 'NITD609' in the English language; one additional article was identified during revision. Nineteen of these in total 43 papers identified reported original studies; 13 of those articles were on pre-clinical studies and 6 reported clinical trials.

RESULTS

A total of 20 studies addressing its preclinical and clinical development have been published on this compound at the time of writing. Cipargamin acts on the PfATP4, which is a P-type Na + ATPase disrupting the Na + homeostasis in the parasite. Cipargamin is a very fast-acting antimalarial, it is active against all intra-erythrocytic stages of the malaria parasite and exerts gametocytocidal activity, with transmission-blocking potential. It is currently undergoing phase 2 clinical trial to assess safety and efficacy, with a special focus on hepatic safety.

CONCLUSION

In the search for novel antimalarial drugs, cipargamin exhibits promising properties, exerting activity against multiple intra-erythrocytic stages of plasmodia, including gametocytes. It exhibits a favourable pharmacokinetic profile, possibly allowing for single-dose treatment with a suitable combination partner. According to the clinical results of the first studies in Asian malaria patients, a possible safety concern is hepatotoxicity.

The Pictet-Spengler Reaction Updates Its Habits

The Pictet-Spengler reaction (P-S) is one of the most direct, efficient, and variable synthetic method for the construction of privileged pharmacophores such as tetrahydro-isoquinolines (THIQs), tetrahydro-β-carbolines (THBCs), and polyheterocyclic frameworks. In the lustro (five-year period) following its centenary birthday, the P-S reaction did not exit the stage but it came up again on limelight with new features. This review focuses on the interesting results achieved in this period (2011-2015), analyzing the versatility of this reaction. Classic P-S was reported in the total synthesis of complex alkaloids, in combination with chiral catalysts as well as for the generation of libraries of compounds in medicinal chemistry. The P-S has been used also in tandem reactions, with the sequences including ring closing metathesis, isomerization, Michael addition, and Gold- or Brønsted acid-catalyzed N-acyliminium cyclization. Moreover, the combination of P-S reaction with Ugi multicomponent reaction has been exploited for the construction of highly complex polycyclic architectures in few steps and high yields. The P-S reaction has also been successfully employed in solid-phase synthesis, affording products with different structures, including peptidomimetics, synthetic heterocycles, and natural compounds. Finally, the enzymatic version of P-S has been reported for biosynthesis, biotransformations, and bioconjugations.

3',4'-Dihydro-2'H-spiro[indoline-3,1'-isoquinolin]-2-ones as potential anti-cancer agents: synthesis and preliminary screening

Both tetrahydroisoquinolines (THIQs) and oxindoles (OXs) display a broad range of biological activities including anti-cancer activity, and are therefore recognized as two privileged scaffolds in drug discovery. In the present study, 24 3',4'-dihydro-2'H-spiro[indoline-3,1'-isoquinolin]-2-ones, designed as molecular hybrids of THIQ and OX, were synthesized and screened in vitro against 59 cell lines in the NCI-60 screen. Twenty compounds displayed weak to moderate inhibition of cell proliferation; among them, three compounds displayed at least 50% inhibition of cell proliferation. The compounds appeared to target primarily renal cell cancer lines; however, leukaemia, melanoma, non-small cell lung cancer, prostate, ovarian and even breast cancer cell lines were also affected. Therefore, this class of spirooxindoles may provide useful leads in the search for new anti-cancer agents.

Synthesis of Chiral Tryptamines via a Regioselective Indole Alkylation

A practical synthesis of chiral tryptamines from simple, unprotected indoles has been developed. Indole nucleophiles prepared with MeMgCl in the presence of CuCl reacted with chiral cyclic sulfamidates almost exclusively at the C³-position of indole to form a variety of α- and/or β-substituted chiral tryptamines in good yield with excellent regioselectivity. The utility of this simple alkylation process has been demonstrated with the practical synthesis of two biologically active targets, cipargamin and TIK-301, which were completed in three steps, starting from the corresponding indole starting materials.

DMAP-catalyzed alkylation of isatin N,N′-cyclic azomethine imine 1,3-dipoles with Morita–Baylis–Hillman carbonates

Metal-free C(sp³)–H alkylation of an isatin N,N′-cyclic azomethine imine 1,3-dipole.

Comprehensive review on various strategies for antimalarial drug discovery

The resistance of malaria parasites to existing drugs carries on growing and progressively limiting our ability to manage this severe disease and finally lead to a massive global health burden. Till now, malaria control has relied upon the traditional quinoline, antifolate and artemisinin compounds. Very few new antimalarials were developed in the past 50 years. Among recent approaches, identification of novel chemotherapeutic targets, exploration of natural products with medicinal significance, covalent bitherapy having a dual mode of action into a single hybrid molecule and malaria vaccine development are explored heavily. The proper execution of these approaches and proper investment from international agencies will accelerate the discovery of drugs that provide new hope for the control or eventual eradication of this global infectious disease. This review explores various strategies for assessment and development of new antimalarial drugs. Current status and scientific value of previous approaches are systematically reviewed and new approaches provide a pragmatic forecast for future developments are introduced as well.

Campisi L, De Crescentini L, Favi G, Mantellini F. Synthesis of novel symmetrical 2-oxo-spiro[indole-3,4′-pyridines] by a reaction of oxindoles with 1,2-diaza-1,3-dienes

Synthesis of symmetrical 2-oxo-spiro[indole-3,4′-pyridines]: a novel example of spirocyclic oxindoles bearing a quaternary centre at the 3-position.

A first-in-human randomized, double-blind, placebo-controlled, single- and multiple-ascending oral dose study of novel Imidazolopiperazine KAF156 to assess its safety, tolerability, and pharmacokinetics in healthy adult volunteers

KAF156 belongs to a new class of antimalarial, the imidazolopiperazines, and is currently in clinical development for the treatment of uncomplicated malaria. This first-in-human, single- and multiple-ascending-dose study in 70 healthy male volunteers determined the maximum oral dose of KAF156 tolerated by healthy adults and derived pharmacokinetic data (including preliminary food effect) to enable dose calculations for malaria patients. KAF156 was studied in single-dose cohorts (10 to 1,200 mg, including one 400-mg food effect cohort (4 to 10 subjects/cohort), and in multiple-dose cohorts (60 to 600 mg once daily for 3 days; 8 subjects/cohort). The follow-up period was 6 to 14 days after the last dose. KAF156 was tolerated, with self-limited mild to moderate gastrointestinal and neurological adverse events. In treated subjects after single doses, headache (n = 4; 11.1%), diarrhea (n = 3; 8.3%), dizziness (n = 3; 8.3%), and abdominal pain (n = 2; 5.6%) were the most common adverse events. Headache (n = 4; 16.7%), nausea (n = 3; 12.5%), upper respiratory tract infection (n = 3; 12.5%), and dizziness (n = 2; 8.3%) were the most common adverse events following multiple doses. KAF156 time to maximum concentration (T_max) was between 1.0 and 6.0 h. Both the area under the concentration-time curve (AUC) and maximum concentration (C_max) increased more than dose-proportionally in both single- and multiple-ascending-dose cohorts (terminal half-life, 42.5 to 70.7 h). There was no significant accumulation over 3-day repeated administration. The extent of absorption was not significantly affected by food at a single dose of 400 mg, while mean C_max decreased from 778 ng/ml to 627 ng/ml and T_max was delayed from a median of 3.0 h under fasting conditions to 6.0 h under fed conditions. Renal elimination is a minor route.

A first-in-human randomized, double-blind, placebo-controlled, single- and multiple-ascending oral dose study of novel antimalarial Spiroindolone KAE609 (Cipargamin) to assess its safety, tolerability, and pharmacokinetics in healthy adult volunteers

This first-in-human randomized, double-blind, placebo-controlled, ascending-single and -multiple oral dose study was designed to evaluate the safety, tolerability, and pharmacokinetics in healthy volunteers of KAE609 (cipargamin; formerly NITD609), a spiroindolone now in trials for malaria treatment. It was studied in single-dose cohorts (1 to 300 mg, including one 30-mg food effect cohort) with 4 to 10 subjects in each cohort and in multiple-dose cohorts (10 to 150 mg once daily for 3 days) with 8 subjects in each cohort. The follow-up period was 6 to 8 days post-last dose. Safety and pharmacokinetics were assessed at scheduled time points during the study. Systemic exposure in terms of the area under the concentration-time curve from 0 h extrapolated to infinity (AUC0-∞) increased in a dose-proportional manner over the dose range of 1 to 300 mg. The AUC from time zero to the time of the last quantifiable concentration (AUClast) and the maximum concentration of drug in plasma (Cmax) also increased in an approximately dose-proportional manner. When administered daily for 3 days, the accumulation ratio on day 3 (the AUC from time zero to 24 h postdosing [AUC0-24] on day 3/AUC0-24 on day 1) was in the range of 1.5 to 2 in the studied dose range (10 to 150 mg) and was consistent with an elimination half-life of around 24 h. Urine analysis for unchanged KAE609 revealed negligible amounts (≤0.01%) were excreted renally. The high fat food intake did not affect the extent of KAE609 absorption (AUC); however, the Cmax was reduced by around 27%. KAE609 was tolerated in this study, with transient gastrointestinal and genitourinary adverse events of mild to moderate intensity (semen discoloration, diarrhea, nausea and abdominal discomfort, dizziness and headache, catheter site hematoma). Gastrointestinal and genitourinary adverse events increased with rising doses.