title: Aminoindoles, a novel scaffold with potent activity against Plasmodium falciparum.
abstract: This study characterizes aminoindole molecules that are analogs of Genz-644442. Genz-644442 was identified as a hit in a screen of ~70,000 compounds in the Broad Institute's small-molecule library and the ICCB-L compound collection at Harvard Medical School. Genz-644442 is a potent inhibitor of Plasmodium falciparum in vitro (50% inhibitory concentrations [IC₅₀s], 200 to 285 nM) and inhibits P. berghei in vivo with an efficacy of > 99% in an adapted version of Peters' 4-day suppressive test (W. Peters, Ann. Trop. Med. Parasitol. 69:155-171, 1975). Genz-644442 became the focus of medicinal chemistry optimization; 321 analogs were synthesized and were tested for in vitro potency against P. falciparum and for in vitro absorption, distribution, metabolism, and excretion (ADME) properties. This yielded compounds with IC₅₀s of approximately 30 nM. The lead compound, Genz-668764, has been characterized in more detail. It is a single enantiomer with IC₅₀s of 28 to 65 nM against P. falciparum in vitro. In the 4-day P. berghei model, when it was dosed at 100 mg/kg of body weight/day, no parasites were detected on day 4 postinfection. However, parasites recrudesced by day 9. Dosing at 200 mg/kg/day twice a day resulted in cures of 3/5 animals. The compound had comparable activity against P. falciparum blood stages in a human-engrafted NOD-scid mouse model. Genz-668764 had a terminal half-life of 2.8 h and plasma trough levels of 41 ng/ml when it was dosed twice a day orally at 55 mg/kg/day. Seven-day rat safety studies showed a no-observable-adverse-effect level (NOAEL) at 200 mg/kg/day; the compound was not mutagenic in Ames tests, did not inhibit the hERG channel, and did not have potent activity against a broad panel of receptors and enzymes. Employing allometric scaling and using in vitro ADME data, the predicted human minimum efficacious dose of Genz-668764 in a 3-day once-daily dosing regimen was 421 mg/day/70 kg, which would maintain plasma trough levels above the IC₉₀ against P. falciparum for at least 96 h after the last dose. The predicted human therapeutic index was approximately 3, on the basis of the exposure in rats at the NOAEL. We were unable to select for parasites with >2-fold decreased sensitivity to the parent compound, Genz-644442, over 270 days of in vitro culture under drug pressure. These characteristics make Genz-668764 a good candidate for preclinical development.
authors.affiliation: Genzyme Corporation, 153 Second Avenue, Waltham, MA 02451, USA. Robert.barker@genzyme.com
authors.forename: Robert H
authors.initials: RH
authors.lastname: Barker
authors.forename: Sameer
authors.initials: S
authors.lastname: Urgaonkar
authors.forename: Ralph
authors.initials: R
authors.lastname: Mazitschek
authors.forename: Cassandra
authors.initials: C
authors.lastname: Celatka
authors.forename: Renato
authors.initials: R
authors.lastname: Skerlj
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Cortese
authors.forename: Erin
authors.initials: E
authors.lastname: Tyndall
authors.forename: Hanlan
authors.initials: H
authors.lastname: Liu
authors.forename: Mandy
authors.initials: M
authors.lastname: Cromwell
authors.forename: Amar Bir
authors.initials: AB
authors.lastname: Sidhu
authors.forename: Jose E
authors.initials: JE
authors.lastname: Guerrero-Bravo
authors.forename: Keila N
authors.initials: KN
authors.lastname: Crespo-Llado
authors.forename: Adelfa E
authors.initials: AE
authors.lastname: Serrano
authors.forename: Jing-Wen
authors.initials: JW
authors.lastname: Lin
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Janse
authors.forename: Shahid M
authors.initials: SM
authors.lastname: Khan
authors.forename: Manoj
authors.initials: M
authors.lastname: Duraisingh
authors.forename: Bradley I
authors.initials: BI
authors.lastname: Coleman
authors.forename: Inigo
authors.initials: I
authors.lastname: Angulo-Barturen
authors.forename: María Belén
authors.initials: MB
authors.lastname: Jiménez-Díaz
authors.forename: Noemí
authors.initials: N
authors.lastname: Magán
authors.forename: Vanesa
authors.initials: V
authors.lastname: Gomez
authors.forename: Santiago
authors.initials: S
authors.lastname: Ferrer
authors.forename: María Santos
authors.initials: MS
authors.lastname: Martínez
authors.forename: Sergio
authors.initials: S
authors.lastname: Wittlin
authors.forename: Petros
authors.initials: P
authors.lastname: Papastogiannidis
authors.forename: Thomas
authors.initials: T
authors.lastname: O'Shea
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Klinger
authors.forename: Mark
authors.initials: M
authors.lastname: Bree
authors.forename: Edward
authors.initials: E
authors.lastname: Lee
authors.forename: Mikaela
authors.initials: M
authors.lastname: Levine
authors.forename: Roger C
authors.initials: RC
authors.lastname: Wiegand
authors.forename: Benito
authors.initials: B
authors.lastname: Munoz
authors.forename: Dyann F
authors.initials: DF
authors.lastname: Wirth
authors.forename: Jon
authors.initials: J
authors.lastname: Clardy
authors.forename: Ian
authors.initials: I
authors.lastname: Bathurst
authors.forename: Edmund
authors.initials: E
authors.lastname: Sybertz
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006801:Humans; D007211:Indoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D051379:Mice; D010962:Plasmodium berghei / Q000187:drug effects; D010963:Plasmodium falciparum / Q000187:drug effects*; D051381:Rats
chemical_list: D000962:Antimalarials; D007211:Indoles