Abiraterone acetate

Search ⌘K Suggest Edit Sign in Sign in Clinical applications Indications and efficacy Dosage and administration Safety and adverse effects Contraindications Handling precautions Common and serious side effects Overdose Drug interactions Drug-drug interactions Food and other interactions Pharmacology Pharmacodynamics Pharmacokinetics Chemistry Chemical structure Synthesis History Discovery and development Regulatory approvals Society and culture Names and formulations Brand names and availability Economics and access Research directions Ongoing clinical trials Investigational uses References Fact-checked by Grok 4 months ago Abiraterone acetate Ara Eve Leo Sal 1x Abiraterone acetate is an orally bioavailable prodrug used primarily to treat advanced prostate cancer , particularly metastatic castration-resistant prostate cancer (mCRPC) and high-risk metastatic castration-sensitive prostate cancer (mCSPC). Sold under the brand name Zytiga, it is administered in combination with a corticosteroid such as prednisone or prednisolone to suppress androgen production that fuels tumor growth despite surgical or medical castration. Upon ingestion, abiraterone acetate is rapidly converted to its active form, abiraterone, which potently and irreversibly inhibits the enzyme cytochrome P450 17α-hydroxylase/17,20-lyase ( CYP17A1 ), thereby blocking the biosynthesis of androgens like testosterone and dihydrotestosterone in the adrenal glands, testes, and intratumoral sites. [1] [2] [3] The development of abiraterone acetate addressed a critical need in prostate cancer management, where tumors often progress to a castration-resistant state due to alternative androgen sources despite androgen deprivation therapy . Preclinical studies demonstrated its ability to reduce androgen levels and inhibit tumor growth in animal models, leading to phase I trials that established a recommended dose of 1000 mg daily. Pivotal phase III clinical trials, including the COU-AA-301 study for post-chemotherapy mCRPC patients, showed significant improvements in overall survival (14.8 months versus 10.9 months with placebo plus prednisone ), prompting FDA approval on April 28, 2011, as the first oral androgen synthesis inhibitor for this indication. Subsequent expansions included approval for chemotherapy-naïve mCRPC in 2012 based on the COU-AA-302 trial and for high-risk mCSPC in 2018 following the LATITUDE and STAMPEDE trials, which confirmed benefits in radiographic progression-free survival and overall survival when added to androgen deprivation therapy . [3] [4] [5] Abiraterone acetate is typically taken as 1000 mg tablets once daily on an empty stomach (at least 1 hour before or 2 hours after food ) to optimize absorption, alongside prednisone 10 mg daily (for example, 5 mg twice daily) to counteract mineralocorticoid-related adverse effects from CYP17 inhibition, such as hypertension and hypokalemia . Common side effects include joint pain or swelling, hot flashes, diarrhea , fatigue, and peripheral edema , while serious risks involve cardiac arrhythmias, liver function abnormalities, and adrenocortical insufficiency, necessitating regular monitoring of blood pressure , electrolytes, and liver enzymes. Recent research as of 2025 has explored lower doses (e.g., 500 mg or less) with food to improve tolerability and reduce costs without compromising efficacy, as well as combinations with PARP inhibitors like niraparib for patients with homologous recombination repair mutations, enhancing progression-free survival in mCSPC. Contraindicated in women (especially pregnant or breastfeeding ) and requiring contraception in men due to teratogenic potential, abiraterone acetate remains a cornerstone of endocrine therapy in metastatic prostate cancer , significantly extending survival in targeted populations. [1] [3] [5] [6] [7] Clinical applications Indications and efficacy Abiraterone acetate is indicated for the treatment of metastatic castration-resistant prostate cancer (mCRPC) in adult men in combination with prednisone or prednisolone. [8] It is also approved for the treatment of metastatic high-risk castration-sensitive prostate cancer (mCSPC) in combination with androgen deprivation therapy (ADT). [5] A fixed-dose combination of abiraterone acetate with the PARP inhibitor niraparib (Akeega), taken with prednisone , is indicated for adults with BRCA-mutated mCRPC who have not previously received a new hormonal agent for mCRPC. [9] Efficacy in mCRPC was established in the phase 3 COU-AA-301 trial , which demonstrated that abiraterone acetate plus prednisone prolonged median overall survival to 14.8 months compared to 10.9 months with placebo plus prednisone in patients post- chemotherapy ( hazard ratio [HR] 0.65; 95% CI 0.54-0.78). [10] In chemotherapy-naïve patients, the COU-AA-302 trial showed improvements in radiographic progression-free survival (rPFS) and overall survival, supporting its use to delay chemotherapy initiation. [8] For high-risk mCSPC, the phase 3 LATITUDE trial reported that abiraterone acetate plus prednisone with ADT reduced the risk of death or disease progression by 53% (HR 0.47; 95% CI 0.39-0.57) compared to placebo plus ADT, with median overall survival of 53 months versus 36.5 months. [11] The STAMPEDE trial similarly showed a 71% reduction in the risk of death at 3 years (HR 0.29; 95% CI 0.25-0.34) when abiraterone acetate plus prednisolone was added to standard-of-care therapy , including ADT, in men with metastatic disease . [12] Patient selection for abiraterone acetate typically includes men with mCRPC who have shown inadequate response to prior androgen receptor-targeted therapies or chemotherapy such as docetaxel , or those with high-risk mCSPC defined by criteria like Gleason score ≥8 or visceral metastases. [8] The indication for mCSPC was expanded in 2018 based on the LATITUDE and STAMPEDE trials, establishing its role in early intervention to improve survival outcomes. [5] Dosage and administration Abiraterone acetate is administered orally in combination with a corticosteroid to manage mineralocorticoid excess. The standard recommended dose for the Zytiga formulation is 1,000 mg (four 250 mg tablets) once daily, taken with prednisone 5 mg orally once daily for metastatic castration-sensitive prostate cancer or 5 mg twice daily for metastatic castration-resistant prostate cancer . [8] For the Yonsa formulation , a micronized version with improved bioavailability , the dose is 500 mg (four 125 mg tablets) once daily in combination with methylprednisolone 4 mg orally twice daily. [13] Tablets should be swallowed whole with a full glass of water . The Zytiga formulation must be taken on an empty stomach , at least 1 hour before or 2 hours after a meal , to ensure consistent absorption, while Yonsa may be taken with or without food, providing greater flexibility. [8] [14] Patients receiving abiraterone acetate should also be on a gonadotropin-releasing hormone analog or have undergone bilateral orchiectomy . [8] Dose adjustments are required for hepatic impairment. In patients with moderate hepatic impairment (Child-Pugh class B), the Zytiga dose should be reduced to 250 mg once daily, and for Yonsa, to 125 mg once daily; treatment should not be initiated in those with severe impairment (Child-Pugh class C). [8] [14] No dose adjustment is necessary for renal impairment. [15] If hepatotoxicity or severe adverse effects occur, dosing should be interrupted and resumed at a reduced level upon resolution, or discontinued if toxicity persists. [8] Monitoring includes baseline and periodic assessments of liver function tests (ALT, AST, and bilirubin ), blood pressure , and serum potassium levels, particularly during the initial months of therapy and as clinically indicated. [8] Treatment is typically continued until disease progression or unacceptable toxicity . [8] The Yonsa micronized formulation , approved in 2018, allows for a lower dose compared to non-micronized versions due to enhanced dissolution and absorption. [13] Safety and adverse effects Contraindications Abiraterone acetate has no absolute contraindications per FDA labeling. However, per EMA guidelines, it is contraindicated in women who are or may become pregnant due to the risk of fetal harm, as demonstrated by animal studies showing adverse developmental effects including reduced fetal weight, decreased survival, and alterations in external genitalia such as decreased ano-genital distance. [16] It is also contraindicated in patients with hypersensitivity to abiraterone acetate or any of its excipients, given reports of anaphylactic reactions including difficulty breathing , swollen face, or rash . [16] Additionally, use is contraindicated in patients with severe baseline hepatic impairment (Child-Pugh Class C), as the drug's hepatic metabolism increases the risk of toxicity in this population. [8] [16] It is contraindicated in combination with radium Ra 223 dichloride due to increased risks of fractures and mortality observed in clinical trials. [17] [16] Warnings and precautions include uncontrolled hypertension , severe cardiovascular disease , and a history of QT interval prolongation, as abiraterone acetate can exacerbate these conditions through mineralocorticoid excess leading to fluid retention, hypokalemia , and potential cardiac arrhythmias. [8] Strong CYP3A4 inducers should be avoided or require dose adjustments due to reduced efficacy and altered pharmacokinetics . [8] The drug is not indicated for use in women, except for female healthcare professionals handling it under appropriate precautions, owing to its mechanism of androgen suppression and lack of clinical data in this population. [8] [16] In pediatric patients, abiraterone acetate is not indicated due to the absence of safety and efficacy data. [8] For elderly patients, while there are no specific contraindications, caution is advised due to higher rates of comorbidities that may amplify risks such as cardiovascular events or hepatic issues. [8] Regarding pregnancy and fertility, abiraterone acetate is teratogenic in animal models at exposures as low as 0.03 times the human clinical exposure, causing embryo-fetal toxicity without human data confirming safety . [8] [18] Males of reproductive potential must use effective contraception during treatment and for three weeks after the last dose to prevent exposure to partners who could become pregnant . [8] [16] Animal studies also indicate potential effects on spermatogenesis , including reduced sperm counts, decreased motility, altered morphology, and decreased weights of reproductive organs, suggesting possible impairment of male fertility . [18] Handling precautions Women who are pregnant, may become pregnant, or women of childbearing potential should not handle abiraterone acetate tablets without wearing protective gloves. The medication can be absorbed through the skin, especially if tablets are broken, crushed, or damaged, potentially causing harm to a developing fetus due to its androgen-suppressing effects. If accidental contact occurs, affected individuals should contact a healthcare provider immediately. Caregivers assisting patients should follow similar precautions, including hand washing before and after handling. These recommendations are based on FDA prescribing information and patient safety guidelines from sources like Mayo Clinic and MedlinePlus. Common and serious side effects Abiraterone acetate commonly causes side effects in more than 10% of patients, primarily due to mineralocorticoid excess from elevated adrenocorticotropic hormone (ACTH) levels, including fatigue (up to 39% incidence), joint pain (arthralgia, 30%), peripheral edema (25-27%), hypertension (8.5-37%), hypokalemia (17-28%), diarrhea (10-18%), and urinary tract infections (12%). [8] Other frequent effects (>10%) encompass nausea, hot flushes, cough, and headache. [8] Serious side effects include hepatotoxicity , with grade 3-4 elevations in alanine aminotransferase (ALT) or aspartate aminotransferase (AST) occurring in approximately 6% of patients across five randomized clinical trials, and rare cases of fulminant hepatitis, acute liver failure , or death reported postmarketing. [8] Adrenal insufficiency may arise, particularly if prednisone co-administration is inadequate, leading to symptoms like fatigue and hypotension . [8] Cardiac events, including arrhythmias, myocardial infarction , and heart failure (2.6% incidence versus 0.9% placebo ), are also notable, with QT prolongation and torsades de pointes observed postmarketing. [8] Bone fractures occur at higher rates with long-term use, especially alongside glucocorticoids or in contraindicated combinations such as with radium Ra 223 dichloride (e.g., 28.6% vs. 11.4% in the ERA-223 trial for mCRPC), contributing to osteoporosis risk; monitoring is recommended in mCSPC settings like the LATITUDE trial. [17] [19] Frequency data from pivotal trials highlight these risks: in the COU-AA-301 trial for post-chemotherapy metastatic castration-resistant prostate cancer , hypertension affected 8.5% and hypokalemia 28% of patients (all grades); in the LATITUDE trial for high-risk metastatic castration-sensitive prostate cancer , hypertension reached 37% and hypokalemia 20% (all grades). [8] Postmarketing surveillance has identified rare allergic reactions, such as allergic alveolitis causing cough and shortness of breath . [20] Management strategies focus on monitoring and intervention: monthly assessment of blood pressure , serum potassium , and fluid retention is recommended, with potassium supplementation and antihypertensives used for mineralocorticoid excess symptoms. [8] Liver function tests (ALT, AST, bilirubin ) should be performed prior to initiation, every two weeks for the first three months, and monthly thereafter, with dose interruption for grade 3-4 hepatotoxicity and discontinuation if levels exceed five times the upper limit of normal (ULN) for ALT/AST or three times ULN for bilirubin . [8] Concomitant prednisone (5-10 mg daily) mitigates some mineralocorticoid and ACTH-related effects but may exacerbate bone loss, necessitating bone density monitoring and consideration of bisphosphonates or denosumab for fracture prevention in at-risk patients. [8] For cardiac risks, patients with preexisting conditions require close electrocardiographic surveillance. [8] Overdose Human experience with overdose of abiraterone acetate is limited, and there is no specific antidote available. [21] Symptoms of overdose are expected to be an exaggeration of the drug's known adverse effects, potentially including severe hypokalemia, hypertension, elevated liver enzymes, fast or irregular heartbeat, lightheadedness, dizziness, fainting, shortness of breath, muscle weakness, and upper abdominal pain or tenderness. [21] [1] Additional risks may involve cardiac arrhythmias due to electrolyte imbalances or mineralocorticoid excess, and in severe cases, potential for adrenal crisis from disrupted steroidogenesis. [21] Management of abiraterone acetate overdose focuses on supportive care, including immediate discontinuation of the drug, intravenous fluids for hydration, electrolyte correction (particularly potassium supplementation for hypokalemia ), and monitoring for arrhythmias, cardiac failure, and liver function abnormalities. [21] Activated charcoal may be administered if ingestion was recent to reduce absorption, but hemodialysis is ineffective due to the drug's high protein binding (>99% to albumin and alpha-1 acid glycoprotein). [21] [22] Patients should be observed for at least 48-72 hours post-overdose to detect delayed complications such as hepatic injury or cardiovascular events. [21] Reported cases of abiraterone acetate overdose are rare and primarily accidental, with post-marketing surveillance indicating mostly transient effects such as liver enzyme elevations that resolve upon discontinuation. [21] For instance, isolated reports describe high-dose ingestions leading to reversible hepatic injury without long-term sequelae when promptly managed. [21] The prognosis for abiraterone acetate overdose is generally favorable with early intervention, as effects are typically reversible following drug cessation and supportive therapy . [21] To prevent overdose, abiraterone acetate is administered as a once-daily dose, and patient education on proper storage (at room temperature , away from children) and adherence to prescribed regimens is essential. [21] [1] Drug interactions Drug-drug interactions Abiraterone acetate, a substrate of CYP3A4 , exhibits pharmacokinetic interactions primarily with modulators of this enzyme. Strong CYP3A4 inhibitors such as ketoconazole result in only a modest 15% increase in abiraterone exposure, with no clinically meaningful impact on its pharmacokinetics . [8] Similarly, ritonavir , another strong CYP3A4 inhibitor, is expected to have minimal effects based on in vitro and analogous data, though coadministration should be monitored for potential subtle increases in exposure. [23] In contrast, strong CYP3A4 inducers like rifampin significantly decrease abiraterone exposure by 55%, potentially reducing efficacy; such combinations should be avoided, or if unavoidable, the abiraterone dose may be increased to twice daily during coadministration. [8] As a potent inhibitor of CYP17 (17α-hydroxylase/C17,20-lyase), abiraterone acetate alters steroidogenesis, leading to interactions with other agents affecting this pathway. Concomitant use with other strong CYP17 inhibitors should be avoided to prevent excessive suppression of androgen synthesis and heightened risk of mineralocorticoid excess. [24] Caution is advised with substrates like dexamethasone, which is commonly coadministered to mitigate mineralocorticoid -related adverse effects; while effective in combination , preclinical data suggest dexamethasone may slightly reduce abiraterone plasma levels, warranting clinical monitoring for efficacy . [25] Specific drug combinations can exacerbate toxicity or compromise therapeutic outcomes. Early case reports suggested potential pharmacodynamic interactions between spironolactone and abiraterone, including androgenic effects at high doses leading to elevated PSA and shortened PFS. However, a 2024 retrospective study in veterans found no compromise in efficacy or survival with coadministration, with possibly better outcomes. Since spironolactone was excluded from pivotal trials, monitoring is advised if used concomitantly. [26] [27] Additionally, abiraterone's induction of hypokalemia increases the risk of QT interval prolongation, particularly when combined with other QT-prolonging agents such as ondansetron ; electrolyte monitoring and ECG assessment are recommended in such cases to mitigate cardiac risks. [8] Clinical recommendations emphasize proactive management in polypharmacy settings. Dose adjustments or alternative therapies are preferred for strong CYP3A4 inducers, while therapeutic drug monitoring may guide use with inhibitors or CYP17-related agents. Abiraterone also inhibits CYP2D6 and CYP2C8, necessitating caution or dose reductions for substrates like dextromethorphan or pioglitazone to prevent toxicity . [8] As of 2025, recent developments include warnings in combinations like Akeega (niraparib/abiraterone acetate), a dual-action tablet approved for BRCA-mutated metastatic castration-resistant prostate cancer . No significant pharmacokinetic interaction occurs between niraparib (a PARP inhibitor ) and abiraterone, but strong CYP3A4 inducers remain contraindicated due to reduced abiraterone efficacy, and monitoring for additive effects on blood pressure and myelosuppression is advised. [28] Food and other interactions Abiraterone acetate must be administered on an empty stomach to ensure consistent drug exposure, with no food consumed for at least two hours before and one hour after the dose, as food significantly increases its bioavailability. High-fat meals can elevate the area under the curve (AUC) by up to 10-fold, while low-fat meals increase it approximately fivefold, potentially leading to higher plasma concentrations and increased risk of toxicity. This food effect arises from enhanced absorption in the gastrointestinal tract when taken with meals, necessitating fasting administration to avoid variability in exposure and adverse events. [8] Grapefruit juice should be avoided during treatment with abiraterone acetate, as it acts as a CYP3A4 inhibitor and can increase drug levels, mimicking certain drug-drug interactions and raising the risk of toxicity . Alcohol consumption may exacerbate hepatotoxicity associated with abiraterone acetate by adding stress to the liver, potentially worsening liver enzyme elevations and related side effects. Smoking has minimal documented impact on abiraterone acetate metabolism, though it is generally advised to avoid tobacco use, as it can intensify overall treatment-related side effects without specific pharmacokinetic alterations. Herbal supplements such as St. John's wort should be avoided, as it induces CYP3A4 and may decrease abiraterone acetate concentrations, reducing efficacy. [1] [29] [30] [1] Patients receiving abiraterone acetate require counseling on proper meal timing to optimize absorption and minimize risks, including instructions to avoid over-the-counter supplements or herbals without consulting a healthcare provider to prevent unintended interactions. Due to potential side effects such as dizziness or fatigue , patients should be advised to refrain from driving or operating machinery if these symptoms occur, ensuring safety during daily activities. When co-administered with prednisone , as is standard, additive gastrointestinal effects may arise, including increased risk of ulcers or irritation, warranting monitoring and possible use of protective agents like proton pump inhibitors. [8] [1] [31] Pharmacology Pharmacodynamics Abiraterone acetate is a prodrug that undergoes rapid deacetylation in vivo to form abiraterone, its active metabolite . Abiraterone acts as an irreversible inhibitor of the enzyme cytochrome P450 17A1 ( CYP17A1 ), also known as 17α-hydroxylase/17,20-lyase, which catalyzes key steps in androgen biosynthesis . By binding to the active site of CYP17A1 , abiraterone blocks the conversion of pregnenolone and progesterone to dehydroepiandrosterone (DHEA) and androstenedione , respectively, thereby suppressing androgen production in the testes, adrenal glands, and intratumoral sites within prostate cancer cells. [22] [32] The antiandrogenic effects of abiraterone stem from this inhibition of androgen synthesis, leading to a profound reduction in serum testosterone levels, typically to castrate levels below 1 ng/dL in patients with castration-resistant prostate cancer . This suppression extends to extragonadal androgen production, including intratumoral sources, without direct antagonism of the androgen receptor (AR). Unlike AR antagonists, abiraterone does not bind to or block the AR itself, relying instead on depleting ligand availability to inhibit AR signaling. [22] [33] [34] CYP17A1 inhibition also results in estrogenic activity due to the accumulation of upstream steroid precursors such as pregnenolone and progesterone. These precursors can be shunted toward estrogen synthesis via aromatase-mediated pathways, potentially elevating estrogen levels and contributing to side effects like hot flashes. Additionally, the blockade promotes mineralocorticoid excess by increasing levels of deoxycorticosterone ( DOC ) and corticosterone , which can cause hypertension , hypokalemia , and fluid retention; these effects are mitigated by co-administration of low-dose prednisone to replace glucocorticoids and suppress adrenocorticotropic hormone (ACTH) drive. [35] [33] [36] Abiraterone demonstrates high affinity for CYP17A1 , with an IC 50 of approximately 2-4 nM for both the 17α-hydroxylase and 17,20-lyase activities, indicating potent inhibition. It exhibits minimal off-target effects on other cytochrome P450 enzymes, underscoring its selectivity for androgen biosynthesis pathways. [37] [32] Pharmacokinetics Abiraterone acetate, a prodrug , is rapidly hydrolyzed by esterases in the intestinal mucosa and liver to its active form, abiraterone, following oral administration . The median time to reach maximum plasma concentration (T max ) of abiraterone is approximately 2 hours (range: 1-3 hours), with steady-state concentrations achieved within 3 days of daily dosing. The absolute oral bioavailability of abiraterone acetate has not been determined due to the absence of an intravenous formulation , but systemic exposure is low and highly variable under fasted conditions, with a marked food effect that can increase abiraterone area under the curve (AUC) by up to 10-fold; therefore, it is recommended to administer on an empty stomach at least 1 hour before or 2 hours after a meal to minimize variability. [8] Abiraterone exhibits extensive distribution throughout the body, with a mean volume of distribution of approximately 19,669 L following intravenous administration in healthy subjects, indicating wide tissue penetration. It is highly bound to plasma proteins (>99%), primarily to albumin and alpha-1 acid glycoprotein. Abiraterone crosses the blood-brain barrier only minimally, limiting its central nervous system exposure. [8] [38] Metabolism of abiraterone occurs predominantly in the liver, where it is converted via cytochrome P450 3A4 ( CYP3A4 ) and sulfotransferase 2A1 (SULT2A1) to inactive metabolites, including abiraterone sulfate and N-oxide abiraterone sulfate, which together account for the majority of circulating metabolites. An active metabolite , Δ 4 -abiraterone, is also formed through a minor pathway and contributes approximately 10% to the overall pharmacological activity by inhibiting additional steroidogenic enzymes. The mean terminal half-life of abiraterone is 12 ± 5 hours. [8] [39] Excretion of abiraterone and its metabolites occurs primarily via the fecal route (88% of the dose), with unchanged abiraterone acetate and abiraterone comprising about 55% and 22% of the fecal content, respectively, while only 5% is eliminated in urine , mostly as metabolites. Following a single oral dose, clearance is consistent with hepatic elimination. [8] In special populations, pharmacokinetics are altered in hepatic impairment: mild impairment increases abiraterone AUC by 1.1-fold with a half-life of 18 hours, moderate impairment by 3.6-fold with a half-life of 19 hours, and severe impairment by 7-fold overall (with a 2-fold increase in unbound fraction), necessitating dose adjustments or avoidance. No clinically significant changes in abiraterone exposure occur in patients with renal impairment, including end-stage renal disease on dialysis. In elderly patients, abiraterone exposure tends to be higher due to age-related reductions in clearance, though no specific dose adjustment is required. [8] [40] Chemistry Chemical structure Abiraterone acetate has the molecular formula C 26 _{26} 26 ​ H 33 _{33} 33 ​ NO 2 _{2} 2 ​ and a molecular weight of 391.6 g/mol. [41] It is a white to off-white, non-hygroscopic, crystalline powder that is highly lipophilic, with an octanol-water partition coefficient (logP) of 5.12, and practically insoluble in water. [42] [43] The pKa of the pyridyl nitrogen is 5.19. [43] Abiraterone acetate features a steroidal scaffold derived from pregnenolone , consisting of an androstane core with a Δ 5 ^{5} 5 - double bond between carbons 5 and 6, an acetate ester at the 3β-position, and a 17-(3-pyridyl) side chain attached at the 17β-position. [41] [44] The stereochemistry includes 3S,8R,9S,10R,13S,14S configuration, with the hydroxy equivalent at 3β and the side chain at 17β. [41] The pyridyl group at C17 is essential for binding to CYP17 ( cytochrome P450 17A1). [45] The acetate ester at C3 functions as a prodrug moiety, which undergoes hydrolysis to yield the active form abiraterone (C 24 _{24} 24 ​ H 31 _{31} 31 ​ NO). [41] A minor isomer , Δ 4 ^{4} 4 -abiraterone, can form through metabolic isomerization of the double bond in the A-ring. [46] Synthesis Abiraterone acetate is synthesized primarily from dehydroepiandrosterone (DHEA), a readily available steroidal precursor, through a multi-step process that introduces the characteristic 3-pyridyl substituent at the C-17 position while protecting functional groups to ensure selectivity. The original synthesis, developed in the 1990s , proceeds via organometallic addition to the 17-ketone, followed by dehydration to form the Δ^{16} double bond essential for the molecule's structure and activity. [47] The process begins with protection of the 3β-hydroxy group in DHEA as the acetate ester , typically achieved by reaction with acetic anhydride in the presence of a base like pyridine or 4-dimethylaminopyridine , yielding dehydroepiandrosterone 3- acetate in high yield (over 90%). This protection prevents unwanted side reactions at the 3-position and facilitates purification in later steps. The 17-ketone of this intermediate then undergoes nucleophilic addition with 3-pyridylmagnesium bromide, a Grignard reagent prepared from 3-bromopyridine and magnesium in tetrahydrofuran or diethyl ether , to form the tertiary alcohol at C-17. The addition occurs stereoselectively due to the steric hindrance of the steroidal framework, predominantly yielding the (17R)- isomer . Subsequent dehydration of this alcohol under acidic conditions (e.g., using p-toluenesulfonic acid in toluene ) eliminates water to generate the 17-(3-pyridyl)-Δ^{16} unsaturation, affording crude abiraterone acetate , which is purified by chromatography or recrystallization to achieve pharmaceutical grade. The overall yield for this route is approximately 20-30%, limited by the dehydration step's potential for side products like over-oxidation. [48] [49] Industrial-scale production, optimized by Janssen Pharmaceutica following their acquisition of rights in the early 2000s , favors palladium-catalyzed cross-coupling reactions to enhance efficiency, scalability, and impurity control. A representative method involves first preparing 17-haloandrosta-5,16-dien-3β-ol acetate (e.g., the 17-iodo derivative) from dehydroepiandrosterone acetate via allylic halogenation or enol triflate formation followed by halide exchange. This vinyl halide then couples with 3-pyridylboronic acid or its pinacol ester via Suzuki-Miyaura reaction, using a palladium catalyst like Pd(dppf)Cl_2 in the presence of a base such as potassium carbonate in a solvent mixture of toluene and water at elevated temperature (80-100°C). This stereospecific coupling directly installs the Δ^{16}-pyridyl moiety without an intermediate alcohol, achieving yields of 70-85% for the key step and overall process yields of 40-50%. Alternative couplings, such as Negishi (zinc-mediated) or Stille (stannane-based), have been explored for specific advantages in reagent stability. [50] [51] Quality control in synthesis emphasizes monitoring impurities, particularly the Δ^4-isomer arising from migration of the Δ^5 double bond under basic or thermal conditions, which is limited to below 0.5% through optimized pH and temperature controls during workup . Chiral purity at the steroidal centers, inherited from enantiopure DHEA, exceeds 99% as verified by HPLC and NMR. The final acetylation , if not performed earlier, confirms the prodrug ester , which improves oral absorption by enhancing lipophilicity and passive diffusion across membranes compared to the free alcohol. Recent innovations include process intensifications using design of experiments (DoE) and quality by design (QbD) principles to minimize solvent use and maximize throughput, with patents post-2020 addressing micronized crystalline forms for better bioavailability without altering the core synthetic route. [51] [52] History Discovery and development Abiraterone acetate was discovered in the early 1990s at the Institute of Cancer Research (ICR) in London , UK , by a team led by Mike Jarman, along with Elaine Barrie and Gerry Potter. The compound, initially known as CB7598, emerged from a screening of pregnenolone analogs aimed at identifying potent inhibitors of the enzyme cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17), which catalyzes key steps in androgen biosynthesis. This effort was inspired by earlier observations that the antifungal drug ketoconazole could suppress androgens but lacked specificity, prompting the search for a targeted alternative to treat prostate cancer by blocking testosterone production. [53] [54] Preclinical studies demonstrated abiraterone's high potency as a CYP17 inhibitor, with in vitro IC50 values of 2-4 nM against the enzyme's hydroxylase and lyase activities in human testicular microsomes. In rodent models, oral administration led to greater than 90% suppression of plasma testosterone levels, alongside reductions in androgen-dependent organ weights, confirming its ability to disrupt steroidogenesis without significant off-target effects on other cytochrome P450 enzymes at therapeutic doses. To improve oral bioavailability due to abiraterone's poor aqueous solubility , the acetate prodrug form was developed, enhancing absorption while maintaining the parent compound's selectivity. [55] [56] [55] Early clinical development began with Phase I trials in the mid-2000s at the ICR and The Royal Marsden Hospital , led by investigators including Ian Judson and Johann de Bono, which confirmed the drug's safety profile and biological activity in patients with castration-resistant prostate cancer (CRPC). These studies showed rapid and profound reductions in serum testosterone and prostate-specific antigen (PSA) levels in castrate men, validating CYP17 inhibition as a viable strategy even in advanced disease. In 2004, Cougar Biotechnology licensed the compound from BTG plc (which had acquired rights from the ICR), enabling accelerated progression into larger trials. [53] [57] [58] Key milestones included the initiation of Phase II trials in 2006, which expanded on Phase I findings by demonstrating clinical responses in chemotherapy-naïve CRPC patients, and Phase III trials starting in 2009, including the pivotal COU-AA-301 study in post-chemotherapy settings. That same year, Johnson & Johnson acquired Cougar Biotechnology for approximately $1 billion, providing resources to complete global development and support regulatory submissions. These efforts culminated in approvals in 2011, marking abiraterone acetate as the first CYP17 inhibitor for clinical use. [59] [60] [61] Development faced challenges, notably a pronounced food effect where meals increased abiraterone exposure by 5- to 10-fold, leading to initial recommendations for administration under fasting conditions to ensure consistent pharmacokinetics and minimize toxicity risks like hypertension and hypokalemia from mineralocorticoid excess. As of 2025, abiraterone acetate remains foundational for the design of next-generation CYP17 inhibitors, influencing ongoing efforts to develop agents with improved selectivity and reduced side effects. [62] [63] Regulatory approvals Abiraterone acetate, marketed as Zytiga, received initial approval from the U.S. Food and Drug Administration (FDA) on April 28, 2011, for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) who had previously received docetaxel chemotherapy , in combination with prednisone . The European Medicines Agency (EMA) granted marketing authorization for Zytiga on September 5, 2011, for the same indication in adult men. [20] In December 2012, the FDA expanded the indication for Zytiga to include patients with mCRPC who had not received prior chemotherapy , based on data from the COU-AA-302 trial demonstrating improved overall survival . [64] Further expansion occurred on February 8, 2018, approving abiraterone acetate with prednisone for high-risk metastatic castration-sensitive prostate cancer (mCSPC), supported by the LATITUDE and STAMPEDE trials showing benefits in radiographic progression-free survival and overall survival . [5] On May 23, 2018, the FDA approved Yonsa, a fine-particle formulation of abiraterone acetate, in combination with methylprednisolone for mCRPC, allowing for reduced tablet burden due to enhanced bioavailability . [13] The fixed-dose combination of abiraterone acetate and niraparib, branded as Akeega, was approved by the EMA on April 19, 2023, with prednisone or prednisolone for BRCA-mutated mCRPC in adults, following results from the MAGNITUDE trial indicating improved radiographic progression-free survival. [65] The FDA approved Akeega on August 11, 2023, for the same indication in patients with deleterious or suspected deleterious BRCA mutations, also based on MAGNITUDE data. [9] Abiraterone acetate was added to the World Health Organization's Model List of Essential Medicines in 2019 as a complementary medicine for mCRPC and remains listed in the 23rd edition (2023) and subsequent updates through 2025. [66] It is approved in over 100 countries worldwide, including Canada , Australia , Japan , and the United Kingdom . Generic versions began entering markets starting around 2019 in the United States following patent resolutions, with approvals for abiraterone acetate tablets in 2020 by companies such as Dr. Reddy's Laboratories ; in India , generics were available shortly after branded launch in 2012; and in the European Union , multiple generics like Abiraterone Accord and Abiraterone Mylan received EMA authorization in 2021. [67] [68] Labeling for abiraterone acetate includes warnings for hepatotoxicity , with monitoring recommendations for liver function; these emphasize the risk of severe liver injury , including rare cases of fulminant hepatitis , requiring discontinuation if ALT or AST exceed 20 times the upper limit of normal. [69] No pediatric exclusivity has been granted, as the drug lacks indications for pediatric use. There have been no major withdrawals or restrictions, though post-marketing pharmacovigilance continues to monitor adverse events such as cardiac toxicities and adrenal insufficiency globally. [9] Society and culture Names and formulations Abiraterone acetate is the International Nonproprietary Name (INN) and United States Adopted Name (USAN) for the acetate ester prodrug of abiraterone, the active moiety that inhibits cytochrome P450 17A1 ( CYP17A1 ). [24] The compound's systematic IUPAC name is [(3S,8R,9S,10R,13S,14S)-10,13-dimethyl-17-(pyridin-3-yl)-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3-yl] acetate , and it is also known by the developmental code name CB-7630 (with CB-7598 referring to the parent abiraterone). [41] [70] Pharmaceutical formulations of abiraterone acetate are designed for oral administration to enhance bioavailability of the poorly soluble active moiety. The original formulation is a 250 mg film-coated tablet, containing excipients such as lactose monohydrate (198.65 mg per tablet), magnesium stearate , microcrystalline cellulose , croscarmellose sodium, colloidal silicon dioxide , and hypromellose for coating. [36] A micronized tablet formulation , with particle sizes reduced to 200–800 nanometers for improved dissolution and reduced food effect, is available as 125 mg tablets (typically dosed at 500 mg daily as four tablets). [13] [71] This micronized form addresses limitations in the conventional tablet by allowing administration without regard to meals while maintaining bioequivalence at lower doses. [72] A fixed-dose combination tablet incorporates abiraterone acetate with the PARP inhibitor niraparib, providing 500 mg abiraterone acetate and 100 mg niraparib per tablet (starting dose of two tablets daily for 1,000 mg