Brexanolone was approved for medical use in the United States in 2019.[11][15] The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.[16] The long administration time, as well as the cost for a one-time treatment, have raised concerns about accessibility for many women.[17]
Medical uses
Brexanolone is used to treat postpartum depression in adult women, administered as a continuous intravenous infusion over a period of 60 hours and essential tremor.[11][18]
Clinical efficacy
Women experiencing moderate to severe postpartum depression when treated with a single dose of intravenous brexanolone display a significant reduction in HAM-D scores which persisted 30 days post-treatment.[19]
Side effects
Side effects of brexanolone include dizziness (10–20%), sedation (13–21%), headache (18%), nausea (10%), dry mouth (3–11%), loss of consciousness (3–5%), and flushing (2–5%).[6][11][9][20] It can produce euphoria to a degree similar to that of alprazolam (3–13% at infusion doses of 90–270 μg over a one-hour period).[6] Serious or severe adverse effects are rare but may include altered state of consciousness, syncope, presyncope, fatigue, and insomnia.[20]
Allopregnanolone is an endogenousinhibitorypregnaneneurosteroid.[10] It is made from pregnenolone, and is a positive allosteric modulator of the action of γ-aminobutyric acid (GABA) at GABAA receptor.[10] Allopregnanolone has effects similar to those of other positive allosteric modulators of the GABA action at GABAA receptor such as the benzodiazepines, including anxiolytic, sedative, and anticonvulsant activity.[10][32][33] Endogenously produced allopregnanolone exerts a neurophysiological role by fine-tuning of GABAA receptor and modulating the action of several positive allosteric modulators and agonists at GABAA receptor.[34]
Allopregnanolone acts as a highly potent positive allosteric modulator of the GABAA receptor.[10] While allopregnanolone, like other inhibitory neurosteroids such as THDOC, positively modulates all GABAA receptor isoforms, those isoforms containing δ subunits exhibit the greatest potentiation.[35] Allopregnanolone has also been found to act as a positive allosteric modulator of the GABAA-ρ receptor, though the implications of this action are unclear.[36][37] In addition to its actions on GABA receptors, allopregnanolone, like progesterone, is known to be a negative allosteric modulator of nACh receptors,[38] and also appears to act as a negative allosteric modulator of the 5-HT3 receptor.[39] Along with the other inhibitory neurosteroids, allopregnanolone appears to have little or no action at other ligand-gated ion channels, including the NMDA, AMPA, kainate, and glycine receptors.[40]
Unlike progesterone, allopregnanolone is inactive at the classical nuclearprogesterone receptor (PR).[40] However, allopregnanolone can be intracellularly oxidized into 5α-dihydroprogesterone, which does act as an agonist of the PR, and for this reason, allopregnanolone can produce PR-mediated progestogenic effects.[41][42] (5α-dihydroprogesterone is reduced to produce allopregnanolone, and progesterone is reduced to produce 5α-dihydroprogesterone). In addition, allopregnanolone was reported in 2012 to be an agonist of the membrane progesterone receptors (mPRs) discovered shortly before, including mPRδ, mPRα, and mPRβ, with its activity at these receptors about a magnitude more potent than at the GABAA receptor.[43][44] The action of allopregnanolone at these receptors may be related, in part, to its neuroprotective and antigonadotropic properties.[43][45] Also like progesterone, recent evidence has shown that allopregnanolone is an activator of the pregnane X receptor.[40][46]
Similarly to many other GABAA receptor positive allosteric modulators, allopregnanolone has been found to act as an inhibitor of L-type voltage-gated calcium channels (L-VGCCs),[47] including α1 subtypesCav1.2 and Cav1.3.[48] However, the threshold concentration of allopregnanolone to inhibit L-VGCCs was determined to be 3 μM (3,000 nM), which is far greater than the concentration of 5 nM that has been estimated to be naturally produced in the human brain.[48] Thus, inhibition of L-VGCCs is unlikely of any actual significance in the effects of endogenous allopregnanolone.[48] Also, allopregnanolone, along with several other neurosteroids, has been found to activate the G protein-coupled bile acid receptor (GPBAR1, or TGR5).[49] However, it is only able to do so at micromolar concentrations, which, similarly to the case of the L-VGCCs, are far greater than the low nanomolar concentrations of allopregnanolone estimated to be present in the brain.[49]
Biphasic actions at the GABAA receptor
Increased levels of allopregnanolone can produce paradoxical effects, including negative mood, anxiety, irritability, and aggression.[50][51][52] This appears to be because allopregnanolone possesses biphasic, U-shaped actions at the GABAA receptor – moderate level increases (in the range of 1.5–2 nmol/L total allopregnanolone, which are approximately equivalent to luteal phase levels) inhibit the activity of the receptor, while lower and higher concentration increases stimulate it.[50][51] This seems to be a common effect of many GABAA receptor positive allosteric modulators.[26][52] In accordance, acute administration of low doses of micronized progesterone (which reliably elevates allopregnanolone levels) has been found to have negative effects on mood, while higher doses have a neutral effect.[53]
Antidepressant effects
The mechanism by which neurosteroid GABAA receptor PAMs like brexanolone have antidepressant effects is unknown.[54] Other GABAA receptor PAMs, such as benzodiazepines, are not thought of as antidepressants and have no proven efficacy,[54] although alprazolam has historically been prescribed for depression.[55][56] Neurosteroid GABAA receptor PAMs are known to interact with GABAA receptors and subpopulations differently than benzodiazepines.[54] GABAA receptor-potentiating neurosteroids may preferentially target δ-subunit–containing GABAA receptors, and enhance both tonic and phasic inhibition mediated by GABAA receptors.[54] It is possible that neurosteroids like allopregnanolone may act on other targets, including membrane progesterone receptors, T-type voltage-gated calcium channels, and others, to mediate antidepressant effects.[54]
Allopregnanolone is a pregnane (C21) steroid and is also known as 5α-pregnan-3α-ol-20-one, 5α-pregnane-3α-ol-20-one,[1][2][3][4][5] 3α-hydroxy-5α-pregnan-20-one, or 3α,5α-tetrahydroprogesterone (3α,5α-THP). It is closely related structurally to 5-pregnenolone (pregn-5-en-3β-ol-20-dione), progesterone (pregn-4-ene-3,20-dione), the isomers of pregnanedione (5-dihydroprogesterone; 5-pregnane-3,20-dione), the isomers of 4-pregnenolone (3-dihydroprogesterone; pregn-4-en-3-ol-20-one), and the isomers of pregnanediol (5-pregnane-3,20-diol). In addition, allopregnanolone is one of four isomers of pregnanolone (3,5-tetrahydroprogesterone), with the other three isomers being pregnanolone (5β-pregnan-3α-ol-20-one), isopregnanolone (5α-pregnan-3β-ol-20-one), and epipregnanolone (5β-pregnan-3β-ol-20-one).
A variety of syntheticderivatives and analogues of allopregnanolone with similar activity and effects exist, including alfadolone (3α,21-dihydroxy-5α-pregnane-11,20-dione), alfaxolone (3α-hydroxy-5α-pregnane-11,20-dione), ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one), hydroxydione (21-hydroxy-5β-pregnane-3,20-dione), minaxolone (11α-(dimethylamino)-2β-ethoxy-3α-hydroxy-5α-pregnan-20-one), Org 20599 (21-chloro-3α-hydroxy-2β-morpholin-4-yl-5β-pregnan-20-one), Org 21465 (2β-(2,2-dimethyl-4-morpholinyl)-3α-hydroxy-11,20-dioxo-5α-pregnan-21-yl methanesulfonate), and renanolone (3α-hydroxy-5β-pregnan-11,20-dione).
The 21-hydroxylated derivative of this compound, tetrahydrodeoxycorticosterone, is an endogenous inhibitory neurosteroid with similar properties to those of allopregnanolone, and the 3β-methyl analogue of allopregnanolone, ganaxolone, is under development to treat epilepsy and other conditions, including post-traumatic stress disorder.[10]
History
In March 2019, brexanolone was approved in the United States for the treatment of postpartum depression (PPD) in adult women,[11][15] the first drug approved by the U.S. Food and Drug Administration (FDA) specifically for PPD.[11]
The efficacy of brexanolone was shown in two clinical studies of participants who received a 60-hour continuous intravenous infusion of brexanolone or placebo and were then followed for four weeks.[11] The FDA approved allopregnanolone based on evidence from three clinical trials, conducted in the United States, (Trial 1/NCT02942004, Trial 3/NCT02614541, Trial 2/ NCT02942017) of 247 women with moderate or severe postpartum depression.[58]
The FDA granted the application for brexanolone priority review and breakthrough therapy designations, and granted approval of Zulresso to Sage Therapeutics, Inc.[11]
It has been suggested that allopregnanolone and its precursor pregnenolone may have therapeutic potential for treatment of various symptoms of alcohol use disorders by restoring deficits in GABAergic inhibition, moderating corticotropin releasing factor (CRF) signaling, and inhibiting excessive neuroimmune activation. Many co-occurring symptoms of ethanol addiction (e.g., anxiety, depression, seizures, sleep disturbance, pain) that are believed to contribute to the downward spiral of the addiction may also be controlled with neuroactive steroids.[62]
Exogenous progesterone, such as oral progesterone, elevates allopregnanolone levels in the body with good dose-to-serum level correlations.[63] Due to this, it has been suggested that oral progesterone could be described as a prodrug of sorts for allopregnanolone.[63] As a result, there has been some interest in using oral progesterone to treat catamenial epilepsy,[64] as well as other menstrual cycle-related and neurosteroid-associated conditions. In addition to oral progesterone, oral pregnenolone has also been found to act as a prodrug of allopregnanolone,[65][66][67] though also of pregnenolone sulfate.[68]
In animal models of traumatic brain injury, allopregnanolone has been shown to reduce inflammation by attenuating the production of proinflammatory cytokines (IL-1β and TNF-α) at 3 h after the injury. It has also been shown to reduce the severity of brain damage and improve cognitive function and recovery.[69]
^ abMeyer HH, Jewgenow K, Hodges JK (February 1997). "Binding activity of 5alpha-reduced gestagens to the progestin receptor from African elephant (Loxodonta africana)". General and Comparative Endocrinology. 105 (2): 164–167. doi:10.1006/gcen.1996.6813. PMID9038248.
^ abFrye C, Seliga A (May 2002). "Olanzapine and progesterone have dose-dependent and additive effects to enhance lordosis and progestin concentrations of rats". Physiology & Behavior. 76 (1): 151–158. doi:10.1016/s0031-9384(02)00689-3. PMID12175598. S2CID38249308.
^ abMahendroo M, Wilson JD, Richardson JA, Auchus RJ (July 2004). "Steroid 5alpha-reductase 1 promotes 5alpha-androstane-3alpha,17beta-diol synthesis in immature mouse testes by two pathways". Molecular and Cellular Endocrinology. 222 (1–2): 113–120. doi:10.1016/j.mce.2004.04.009. PMID15249131. S2CID54297812.
^Rougé-Pont F, Mayo W, Marinelli M, Gingras M, Le Moal M, Piazza PV (July 2002). "The neurosteroid allopregnanolone increases dopamine release and dopaminergic response to morphine in the rat nucleus accumbens". The European Journal of Neuroscience. 16 (1): 169–173. doi:10.1046/j.1460-9568.2002.02084.x. PMID12153544. S2CID9953445.
^Terán-Pérez G, Arana-Lechuga Y, Esqueda-León E, Santana-Miranda R, Rojas-Zamorano JÁ, Velázquez Moctezuma J (October 2012). "Steroid hormones and sleep regulation". Mini Reviews in Medicinal Chemistry. 12 (11): 1040–1048. doi:10.2174/138955712802762167. PMID23092405.
^Patte-Mensah C, Meyer L, Taleb O, Mensah-Nyagan AG (February 2014). "Potential role of allopregnanolone for a safe and effective therapy of neuropathic pain". Progress in Neurobiology. 113: 70–78. doi:10.1016/j.pneurobio.2013.07.004. PMID23948490. S2CID207407077.
^Reddy DS, Rogawski MA, Rogawski MA, Olsen RW, Delgado-Escueta AV, Reddy DS, Rogawski MA (2012). "Neurosteroids — Endogenous Regulators of Seizure Susceptibility and Role in the Treatment of Epilepsy". Jasper's Basic Mechanisms of the Epilepsies, 4th Edition: 984–1002. doi:10.1093/med/9780199746545.003.0077. ISBN9780199746545. PMID22787590.
^Kokate TG, Svensson BE, Rogawski MA (September 1994). "Anticonvulsant activity of neurosteroids: correlation with gamma-aminobutyric acid-evoked chloride current potentiation". The Journal of Pharmacology and Experimental Therapeutics. 270 (3): 1223–1229. PMID7932175.
^Pinna G, Uzunova V, Matsumoto K, Puia G, Mienville JM, Costa E, Guidotti A (January 2000). "Brain allopregnanolone regulates the potency of the GABA(A) receptor agonist muscimol". Neuropharmacology. 39 (3): 440–448. doi:10.1016/S0028-3908(99)00149-5. PMID10698010. S2CID42753647.
^Lamba V, Yasuda K, Lamba JK, Assem M, Davila J, Strom S, Schuetz EG (September 2004). "PXR (NR1I2): splice variants in human tissues, including brain, and identification of neurosteroids and nicotine as PXR activators". Toxicology and Applied Pharmacology. 199 (3): 251–265. Bibcode:2004ToxAP.199..251L. doi:10.1016/j.taap.2003.12.027. PMID15364541.
^ abKeitel V, Görg B, Bidmon HJ, Zemtsova I, Spomer L, Zilles K, Häussinger D (November 2010). "The bile acid receptor TGR5 (Gpbar-1) acts as a neurosteroid receptor in brain". Glia. 58 (15): 1794–1805. doi:10.1002/glia.21049. PMID20665558. S2CID37368754.
^ abBäckström T, Haage D, Löfgren M, Johansson IM, Strömberg J, Nyberg S, et al. (September 2011). "Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons". Neuroscience. 191: 46–54. doi:10.1016/j.neuroscience.2011.03.061. PMID21600269. S2CID38928854.
^ abAndréen L, Nyberg S, Turkmen S, van Wingen G, Fernández G, Bäckström T (September 2009). "Sex steroid induced negative mood may be explained by the paradoxical effect mediated by GABAA modulators". Psychoneuroendocrinology. 34 (8): 1121–1132. doi:10.1016/j.psyneuen.2009.02.003. PMID19272715. S2CID22259026.
^Andréen L, Sundström-Poromaa I, Bixo M, Nyberg S, Bäckström T (August 2006). "Allopregnanolone concentration and mood--a bimodal association in postmenopausal women treated with oral progesterone". Psychopharmacology. 187 (2): 209–221. doi:10.1007/s00213-006-0417-0. PMID16724185. S2CID1933116.
^Warner MD, Peabody CA, Whiteford HA, Hollister LE (April 1988). "Alprazolam as an antidepressant". The Journal of Clinical Psychiatry. 49 (4): 148–150. PMID3281931.
^ abAndréen L, Spigset O, Andersson A, Nyberg S, Bäckström T (June 2006). "Pharmacokinetics of progesterone and its metabolites allopregnanolone and pregnanolone after oral administration of low-dose progesterone". Maturitas. 54 (3): 238–244. doi:10.1016/j.maturitas.2005.11.005. PMID16406399.
^Piper T, Schlug C, Mareck U, Schänzer W (May 2011). "Investigations on changes in ¹³C/¹²C ratios of endogenous urinary steroids after pregnenolone administration". Drug Testing and Analysis. 3 (5): 283–290. doi:10.1002/dta.281. PMID21538944.
Clinical trial number NCT02942004 for "A Study to Evaluate Efficacy and Safety of SAGE-547 in Participants With Severe Postpartum Depression (547-PPD-202B)" at ClinicalTrials.gov
Clinical trial number NCT02614547 for "A Study to Evaluate SAGE-547 in Patients With Severe Postpartum Depression" at ClinicalTrials.gov
Clinical trial number NCT02942017 for "A Study to Evaluate Safety and Efficacy of SAGE-547 in Participants With Moderate Postpartum Depression (547-PPD-202C)" at ClinicalTrials.gov