Table 2.

Effects of select RAMBAS on ATRA metabolism in animal models and pharmacological outcomes of animal studies

Ketoconazole (KTZ)
Dose	Animal model	Pharmacological Effects	Ref.
2.5 – 40 mg/kg KTZ po 1 hr prior to iv injection of 200 ng [3H]RA	Male and female Wistar rats	40 mg/kg KTZ inhibited the formation of polar RA metabolites compared to vehicle treated control at all time points between 10 and 120 min; 2.5 – 10 mg/kg KTZ partially suppressed the formation polar RA metabolites; 20 mg/kg and 40 mg/kg suppressed RA metabolism by 75%; 1–2 hr pre-treatment had the most inhibitory effect with decreasing effect with increasing pre-treatment times	[182]
40 mg/kg KTZ po 1 hr prior to iv injection of 0.1 mg/kg RA	Male Wistar rats	KTZ increased the plasma AUC and t1/2 of RA and decreased the clearance; KTZ increased endogenous plasma RA from non-detectable (<0.5 ng/mL) to 1.3 ng/mL at 2 hrs	[94]
320 mg/kg KTZ po and 0.48 mg/hr•kg RA	Male Wistar rats	Increased RA Cmax and Tmax more than 1.3-fold and increased AUC more than 2.6-fold	[183]
Liarozole (LRZ)
Dose	Animal model	Pharmacological Effects	Ref.
40, 80, 120, and 160 mg LRZ per 100 g food for 72 d.	Intact and castrated male Copenhagen × Fisher F1 rats bearing R3327G sc implanted tumor	Doses of 80 mg and above were as effective as castration at reducing tumor weight; testes, prostate, and seminal vesicles were less effected by LRZ than castration; increased LH; LRZ was effective despite testosterone supplementation	[94]
5 and 10 mg LRZ per 100 g food for 28 d.	Androgen-independent MatLu prostatic adenocarcinoma injected sc in intact and castrated male rats	LRZ reduced tumor volume by 79% and 72% for 5 and 10 mg doses; castration had no effect	[90]
20, 40 or 80 mg/kg po	Skin carcinogenesis induced by DMBA in female CD-1 mice	Reduced tumor incidence and tumor burden	[91]
0.3, 1.25, 5, and 20 mg/kg po	Female Wistar rats	Increased endogenous plasma RA from undetectable (<0.5 ng/mL) to 1.4 and 1.9 ng/mL for 5 and 20 mg/kg doses	[91]
20 mg/kg po	Ovariectomized female Wistar rats challenged with estradiol undecylate	LRZ treatment completely inhibited vaginal keratinization similar to RA (20 mg/kg); reduced 57–60 kDa keratin and increased 45–47 kDa keratin protein expression similar to RA (20 mg/kg)	[93]
40 mg/kg LRZ po 1 hr prior to iv injection of 0.1 mg/kg RA	Male Wistar rats	LRZ increased the plasma AUC and t1/2 of RA and decreased clearance more than 2.5-fold; LRZ increased endogenous plasma RA from non-detectable (<0.5 ng/mL) to 2.5 ng/mL at 2 hrs with RA detectable at all time points between 0.5 and 6 hrs	[93]
40 mg/kg po	Mice injected sc with PC-3 tumor cells	Prevented tumor incidence in all but two of the mice inoculated 5 or 10 d. prior; Reduced collagenase IV levels in PC-3 ML-B tumors	[184]
40 mg/kg LRZ dosed 15 min prior to 10 mg/kg ATRA or 9-cisRA	Male Balb/c nude mice	LRZ significantly increased ATRA mean peak plasma levels, Tmax, and plasma AUC after first dose and to a lesser extent 2 d. later; LRZ had less of an effect on 9-cisRA, only increased AUC after second dose	[185]
20 to 120 mg LRZ/100 g food	Male Copenhagen × Fisher F1 rats bearing Dunning androgen-dependent and -independent prostate tumors	Inhibited the growth of androgen-dependent (H and G sublines) and androgen-independent (PIF-1 and AT-6 sublines) tumors but not the androgen-independent AT-6 sq tumor	[186]
40 mg/kg LRZ 1 hr prior to 20 μg 4-keto-atRA	Male Wistar rats	Pretreatment with LRZ inhibited the metabolism of 4-keto-RA; Almost doubled t1/2	[113]
Decreasing dose of 80, 60, 30, 15, 7.5, and 3.75 mg/kg po, bid	Male Copenhagen × Fisher F1 rats bearing Dunning AT-6sq androgen-independent prostate tumor	Reduced mean tumor weight at all doses; significantly increased plasma RA concentrations; Dose-related RA accumulation of RA above 7.5 mg/kg	[187]
20 mg/kg or 80 mg/kg LRZ with and without 100 μg/kg tamoxifen	Female Sprague-Dawley rats bearing MNU-induced mammary tumors	LRZ stopped tumor growth; When combined with tamoxifen, LRZ led to tumor shrinkage while inhibiting the uterotrophic effect of tamoxifen	[188]
Talarozole (TLZ)
Dose	Animal model	Pharmacological Effects	Ref.
2.5 mg/kg po	Male and female Wistar rats	Mean RA levels in plasma, skin, fat, kidney, and spleen were significantly elevated 2- to 4-fold from 2 to 8 hrs; Liver RA levels were significantly elevated 1.4-fold at 6 hrs; RA levels returned to baseline in all tissues by 18 hrs; elevated liver CYP26A1 mRNA expression after 4 d. and induction was reduced when RAR antagonist AGN193109 was co-administered; Cp of TLZ ranged from 14.8 to 67.7 ng/mL over 8 hrs	[133]
0.04 – 10 mg/kg TLZ or 0.6 –20 mg/kg RA for 3 d.	Estrogen-exposed ovariectomized female Wistar rats	TLZ inhibited vaginal keratinization with ED50 of 1 mg/kg; RA had ED50 of 5.1 mg/kg; co-adminstration of the RAR antagonist AGN193109 reduced keratinization	[133]
2.5 mg/kg TLZ or 2.5 mg/kg RA for 14 d.	Female skh: HR1 hairless mice	TLZ and RA increased thickness of pinnal epidermis ~2-fold; TLZ and RA increased the percentage of tail orthokeratosis from 30.3% to 90%	[133]
Other RAMBAs in development
Dose	Animal model	Pharmacological Effects	Ref.
0.033 μmol/kg/d. compound 1a, 6 d./week for 6 weeks	Ovariectomized nude mice bearing MCF-7 tumor xenografts	85.2% reduction in the mean final tumor volume compared to vehicle-treated control mice	[142]
0.033 μmol/kg/d. of compounds 1, 3, and 4 for 6 weeks	Male SCID mice bearing LNCaP tumor xenografts	Tumor growth with compound 1a was similar to vehicle-treated control; Compounds 3 and 4 reduced tumor growth by 44% and 47%, respectively; No effect on body weight	[157]
16.5, 33 or 66 μmol/kg/d. compound 1a and 66 μmol/kg/d. compound 3 for 6 weeks	Ovariectomized female athymic nude mice bearing MCF-7 tumor xenografts	Compound 1a had a dose-dependent inhibition of tumor growth (66.5%, 79.4%, and 92.6%); Compound 3 had an effect similar to 20 mg/kg ATRA on growth inhibition; Compound 1a inhibited growth 120% when combined with 33 μmol/kg/d. ATRA	[159]
5, 10, or 20 mg/kg/d. compound 1a po, 5 d./week for 8 weeks	Female Sprague-Dawley rats bearing MNU-induced mammary tumors	Compound 1a reduced mean tumor volume and increased tumor apoptosis in a dose-dependent manner; Increased plasma RA concentration in dose-dependent manner (from 0.71 ng/ml in control to 5.16 ng/ml with highest dose of compound 1a)	[160]
2.5 or 5 mg/kg compound 1b or 5 mg/kg ATRA alone or with 50 mg/kg chloroquine sc, biw	Female SCID mice bearing SKBR-3 tumor xenografts	5 mg/kg compound 1b alone or with chloroquine was more effective than ATRA or 2.5 mg/kg compound 1b at inhibiting tumor growth; compound 1b was more effective in combination with chloroquine (92.6% growth inhibition vs 81.4% alone)	[163]
2.5 or 5 mg/kg sc biw or 10 or 20 mg/kg sc qd of compound 1b or ATRA with or without 50 mg/kg sc biw chloroquine	Female SCID mice	Two highest doses of compound 1b were toxic (75% and 100% mortality rates); Severity of alopecia and skin scaling increased with dose; PK data based on 20 mg/kg sc; Cmax = 41.38 μg/ml, tmax = 2 h, t1/2 = 6 h, AUC 83.78 h•μg/ml; Three polar metabolites were observed, with one being identified as compound 1a; AUC of all metabolites 89.24 h•μg/ml	[189]
0.08 – 1.25 mg/kg R116010 or 1.25–5 mg/kg RA po, bid for 21 d.	Mice inoculated with oestrogen-independent TA3-Ha carcinoma cells	0.16 mg/kg R116010, bid was lowest effective dose to inhibit tumor growth, with toxicity at 5 mg/kg, bid; 2.5 mg/kg RA, bid was lowest effective dose with toxicity at 5 mg/kg, bid	[190]
10 mg/kg compound 9 with 5 mg/kg ATRA	Female CD-1 mice	Inhibitor increased the plasma AUC of ATRA by 5.9-fold and increased ATRA half-life	[170]