Fig 1.
Rabbit plasma and brain concentration-time profiles of allopregnanolone following intravenous (IV) bolus or transdermal (TD) administration.
A. Dosing at 3 mg/kg IV bolus using 1.5 mg/ml Allo solution in 20% HBCD in nine female New Zealand rabbits (n = 1–9 per time point) and B. Dosing 5 mg/kg TD using 20 mg/ml Allo solution in DMSO administered to nine adult female New Zealand rabbits (n = 1–9 per time point). Data points represented as mean ± SD. LLOQ: Lower Limit of Quantification.
Fig 2.
Mouse plasma and brain concentration-time profiles of allopregnanolone following intravenous (IV), subcutaneous (SC) and transdermal (TD) administration.
A. Dosing at 1.5 mg/kg IV using Allo solution in 6% HBCD vehicle in male non-transgenic mice (15-months-old, n = 5–6). B. Dosing at 10 mg/kg SC using Allo suspension in 5% EtOH/PBS vehicle in male non-transgenic mice (15-months-old, n = 1–3), at 10 mg/kg SC using Allo suspension in 5% EtOH/PBS vehicle in male 3xTgAD mice (5-months-old, n = 6) and 50 mg/kg TD using Allo solution 45% DMSO, 30% EtOH, 2.5% Klucel MF, 19.2% PEG-300 (5-months-old, n = 8). Data points represented as mean ± SD. LLOQ: Lower Limit of Quantification.
Table 1.
Pharmacokinetic parameters for allopregnanolone in both rabbit and mouse.
Fig 3.
Subcutaneous Allo increased BrdU incorporation and PCNA protein expression in male mouse AD model.
A. In 5-month-old 3xTgAD mouse hippocampus, BrdU+ nuclei increased significantly in 24 h after a single subcutaneous (SC) dose of Allo 0.5, 1, or 10 mg/kg. B. In 5-month-old 3xTgAD mouse hippocampus, protein expression of ~29 kDa PCNA increased significantly at 24 h after SC Allo 0.5 and 1 mg/kg doses whereas 10 mg/kg dose trended towards increase but did not reach significance. Transdermal and subcutaneous Allo increased PCNA protein expression in male mouse AD model. C. In 5-month-old 3xTgAD mouse hippocampus, protein expression of PCNA increased significantly at 4 h after transdermal (TD) Allo 50 mg/kg and SC Allo 10 mg/kg doses. D. In 15-month-old nonTg mouse hippocampus, protein expression of PCNA increased significantly at 4 h after TD Allo 50 mg/kg dose. E. In 5-month-old 3xTAD and 15-month-old nonTg mouse hippocampus, BrdU+ nuclei increased significantly in 24 h after intranasal (IN) dose of Allo 3 mg/kg 100% Castor Oil and Allo 10 mg/kg 20% HBCD suspension doses. F. In 5-month-old 3xTgAD and 15-month-old nonTg mouse hippocampus, protein expression of PCNA increased significantly at 24 h after IN Allo 3 mg/kg 100% Castor Oil and Allo 10 mg/kg 20% HBCD suspension doses. Intramuscular Allo-induced increase in cell cycle marker in male mouse AD model. G. In 5-month-old 3xTgAD mouse hippocampus, BrdU+ nuclei increased significantly in 24 h after a single intramuscular (IM) dose of Allo 2 mg/kg and SC Allo 10 mg/kg dose. H. In 5-month-old 3xTgAD mouse hippocampus, protein expression of PCNA increased significantly at 24 h post-IM Allo 2 mg/kg dose and SC Allo 10 mg/kg dose. Intravenous Allo-induced increase in cell cycle and neurodifferentiation markers in male mouse AD model. I. In 5-month-old 3xTgAD mouse hippocampus, protein expression of 30 kDa cyclinD2 increased significantly at 4 h post-intravenous (IV) Allo 0.1 and 0.5 mg/kg dose whereas 1 mg/kg dose trended towards increase but did not reach significance. J. In 5-month-old 3xTgAD mouse hippocampus, protein expression of PCNA increased significantly at 4 h after IV Allo 0.5 mg/kg dose whereas 0.1 and 1 mg/kg dose did not reach significance. K. In 5-month-old 3xTgAD mouse hippocampus, protein expression of ~40 kDa doublecortin (DCX) increased significantly at 4 h after IV Allo 0.5 and 1 mg/kg doses. L. In 5-month-old 3xTgAD mouse hippocampus, protein expression of 49 kDa NeuroD increased significantly at 4 h after IV Allo 0.5 mg/kg, whereas 0.1 and 1 mg doses did not reach significance. Intravenous Allo-induced rapid transient increase in CREB phosphorylation in male mouse aging model. M. In 15-month-old nonTg mouse hippocampus, protein expression of 43 kDa serine 133 phosphorylated CREB (pCREB) increased significantly 5 min after IV Allo 1.5 mg/kg dose. N. In 15-month-old nonTg mouse hippocampus, protein expression of 49 kDa NeuroD1 (NeuroD) increased significantly at 4 h then decreased at 24 h after intravenous Allo 1.5 mg/kg dose. * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001, n = 4–6, bars represent mean value ± SEM.
Table 2.
Summary of mouse efficacy data and statistical comparisons.
Fig 4.
Formulation development, route of administration, and rat behavioral task study components.
Study design. A. Four different formulations were administered by subcutaneous (SC) route to male rats at the maximally tolerated dose (MTD) for sedation, determined to be 8 mg/kg for the leading formulation Allo 6 mg/ml, 24% sulfobutyl-ether-β-cyclodextrin sodium (SBECD). Optimal release rate formulations for SC were then tested via dose-response for SC, intramuscular (IM), and intravenous (IV) routes using the rat balance beam behavioral task to score motor incoordination due to Allo-induced sedation, a biomarker of Allo target engagement and tolerability. Sedation score as a biomarker of Allo target engagement. B. The sedative component of GABAA receptor activation in the brain was used as a biomarker outcome of Allo delivery and tolerability. Male rats (Age 7 months at study initiation) were dosed by SC route of administration with multiple formulations, to determine effect on sedation. Doses were administered at Allo 8 mg/kg SC to compare sedation responses at 5 min intervals. The formulations were of either Allo solutions or suspensions (in 0.9% sodium chloride with SBECD) designed to determine the Allo delivery rate as it relates to SBECD:Allo molar ratio. Balance Beam Behavioral Scoring System: 4 = reach platform; 3 = takes steps; 2 = all paws on top; 1 = clasp; 0 = fall. n = 4, interval points represent mean value ± SEM. Area bound by sedation curve as an indicator of rapid Allo target engagement. C. The area bound by the sedation curve (AUCsed; area above the curve as graphically represented) was calculated to determine the sedative component of GABAA receptor activation in the brain as an indicator of Allo delivery. Male rats (Age 7 months at study initiation) were administered Allo 8 mg/kg SC bolus to compare delivery of multiple formulations of either Allo solutions or suspensions (in 0.9% sodium chloride with SBECD) designed to determine the Allo delivery rate as it relates to SBECD:Allo molar ratio. Area bound by sedation curve was calculated and expressed as behavioral score (a score between 4 and 0) multiplied by minutes post-treatment. n = 4, bars represent mean value ± SEM.
Table 3.
Summary of rat sedation data and statistical comparisons.
Fig 5.
Allopregnanolone (Allo) dose-response comparison by subcutaneous (SC), intramuscular (IM), and intravenous (IV) routes of administration.
Ovariectomized female rats (left panel) were compared to age-matched male rats (right panel) following SC (A. and B.), IM (C. and D.), or IV (E. and F.) bolus injection and challenged with a motor coordination behavioral task to assess level of sedation at timed intervals until recovery. SC/IM formulation: 6 mg/ml Allo solution in 0.9% sodium chloride with 24% sulfobutyl ether β-cyclodextrin sodium (SBECD). IV formulation: 1.5 mg/ml Allo solution in 0.9% sodium chloride with 6% SBECD. The volume of vehicle administered was equal to the volume administered with the highest dose, i.e. 8 mg/kg (SC/IM) or 2 mg/kg (IV). Balance Beam Behavioral Scoring System: 4 = reach platform; 3 = takes steps; 2 = all paws on top; 1 = clasp; 0 = fall. n = 4, interval points represent mean value ± SEM. Area bound by sedation curve as an indicator of rapid Allo target engagement. G. The area bound by the sedation curve (above the curve; Fig 5A–5F) (AUCsed) was calculated to determine the sedative component of GABAA receptor activation in the brain as an indicator of Allo delivery. AUCsed was calculated and expressed as behavioral score (a score between 4 and 0) multiplied by minutes post-treatment. Sex differences in the Allo-induced sedation response were determined. * p<0.05, ** p<0.01, n = 4, bars represent mean value ± SEM.
Table 4.
Allopregnanolone equivalent doses in mouse, rat, rabbit, and human.
Table 5.
Estimation of allopregnanolone no observable adverse effect level (NOAEL) and maximally tolerated dose (MTD) in male and female rats and predicted human NOAEL and MTD by multiple routes of administration.