Steroidal Aromatase Inhibitors Research Articles

Lipid changes during endocrine therapy in early-stage breast cancer patients: A real-world study

BackgroundEndocrine drugs may affect lipid metabolism in breast cancer (BC) patients. This study explores lipid changes in early-stage BC patients taking different endocrine drugs.MethodsThe changing trend of blood lipid during endocrine therapy in 2756 BC patients from January 2013 to December 2021 was retrospectively analyzed. The changes in four lipid parameters were assessed by the Generalized Linear Mixed Model, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL-C), and high-density lipoprotein (HDL-C). These parameters were quantified at baseline and at 6, 12, 18, 24, 36, 48, 60, and 72 months after endocrine therapy initiation. Furthermore, a subgroup analysis according to menopausal status or medication types was conducted.ResultsA total of 1201 patients taking aromatase inhibitors (AIs), including anastrozole (ANA), letrozole (LET), or exemestane (EXE), and 1555 patients taking toremifene (TOR) were enrolled. TC and TG levels showed a significantly elevated trend during 5 years of treatment (P < 0.05). HDL-C levels increased from baseline in the TOR group (P < 0.05). Compared with the postmenopausal AI group, the increasing trends of TC, TG, and LDL-C in the premenopausal AI group were more evident with the extension of time (β = 0.105, 0.027, 0.086, respectively). Within 3 years, TC, TG, and LDL-C levels in the ANA and LET groups were significantly higher than baseline (P < 0.05). Moreover, the levels of TG in the EXE group were significantly lower than that in the ANA or LET group (P < 0.05), but this significant difference disappeared after 3 years.ConclusionsAIs significantly influenced lipid profiles more than TOR. AIs had a greater effect on blood lipids in premenopausal patients. Steroidal AIs (EXE) may affect lipid levels less than nonsteroidal AIs (ANA and LET).

In Vitro Effects of Combining Genistein with Aromatase Inhibitors: Concerns Regarding Its Consumption during Breast Cancer Treatment.

The third-generation of aromatase inhibitors (AIs)-Exemestane (Exe), Letrozole (Let), and Anastrozole (Ana)-is the main therapeutic approach applied for estrogen receptor-positive (ER+) breast cancer (BC), the most common neoplasm in women worldwide. Despite their success, the development of resistance limits their efficacy. Genistein (G), a phytoestrogen present in soybean, has promising anticancer properties in ER+ BC cells, even when combined with anticancer drugs. Thus, the potential beneficial effects of combining G with AIs were investigated in sensitive (MCF7-aro) and resistant (LTEDaro) BC cells. The effects on cell proliferation and expression of aromatase, ERα/ERβ, and AR receptors were evaluated. Unlike the combination of G with Ana or Let, which negatively affects the Ais' therapeutic efficacy, G enhanced the anticancer properties of the steroidal AI Exe, increasing the antiproliferative effect and apoptosis relative to Exe. The hormone targets studied were not affected by this combination when compared with Exe. This is the first in vitro study that highlights the potential benefit of G as an adjuvant therapy with Exe, emphasizing, however, that soy derivatives widely used in the diet or applied as auxiliary medicines may increase the risk of adverse interactions with nonsteroidal AIs used in therapy.

Formulation and evaluation of self-nanoemulsifying drug delivery system for improved oral delivery of exemestane hydrochloride

Exemestane HCl (EXM) is a new irreversible steroidal aromatase inhibitor for adjuvant therapy of hormonally sensitive breast cancer in post-menopausal women. EXM's low water solubility hinders solid oral dosage form development. The current work aims to increase EXM solubility by formulating the self nanoemulsifying drug delivery (SNEDDs) system. The water titration approach was employed in the development of SNEDDs. Based on solubility tests, SNEDDs components Caprol Microexpress and Labrafac were selected as oil phase, Tween 80 as surfactant, and Triacetin as co-surfactant. Phase investigations were carried out with various surfactant:co-surfactant ratios (1:1, 1:2, 1:3, 2:1, 3:1). Tween 80: triacetin (1:2) and (1:3) with Caprol Microexpress and Labrafac alone had the greatest nanoemulsion area. Visual evaluation, optical clarity, particle size, medication concentration, and viscosity were used to optimise 10 formulations. F3, F7, and F8 batches had the lowest size at 7.313 ± 1.44 nm, 6.379 ± 0.45 nm, and 14.67 ± 0.37 nm, respectively, with self-emulsification times under 1 min.But optical clarity data was suggested that F7 was not showing any precipitation up to 24 H. Overall, the developed SNEDDS formulation could be a promising approach for the improved oral delivery of EXE with enhanced dissolution and bioavailability.

An Exemestane Derivative, Oxymestane-D1, as a New Multi-Target Steroidal Aromatase Inhibitor for Estrogen Receptor-Positive (ER+) Breast Cancer: Effects on Sensitive and Resistant Cell Lines.

Around 70-85% of all breast cancer (BC) cases are estrogen receptor-positive (ER+). The third generation of aromatase inhibitors (AIs) is the first-line treatment option for these tumors. Despite their therapeutic success, they induce several side effects and resistance, which limits their efficacy. Thus, it is crucial to search for novel, safe and more effective anti-cancer molecules. Currently, multi-target drugs are emerging, as they present higher efficacy and lower toxicity in comparison to standard options. Considering this, this work aimed to investigate the anti-cancer properties and the multi-target potential of the compound 1α,2α-epoxy-6-methylenandrost-4-ene-3,17-dione (Oxy), also designated by Oxymestane-D1, a derivative of Exemestane, which we previously synthesized and demonstrated to be a potent AI. For this purpose, it was studied for its effects on the ER+ BC cell line that overexpresses aromatase, MCF-7aro cells, as well as on the AIs-resistant BC cell line, LTEDaro cells. Oxy reduces cell viability, impairs DNA synthesis and induces apoptosis in MCF-7aro cells. Moreover, its growth-inhibitory properties are inhibited in the presence of ERα, ERβ and AR antagonists, suggesting a mechanism of action dependent on these receptors. In fact, Oxy decreased ERα expression and activation and induced AR overexpression with a pro-death effect. Complementary transactivation assays demonstrated that Oxy presents ER antagonist and AR agonist activities. In addition, Oxy also decreased the viability and caused apoptosis of LTEDaro cells. Therefore, this work highlights the discovery of a new and promising multi-target drug that, besides acting as an AI, appears to also act as an ERα antagonist and AR agonist. Thus, the multi-target action of Oxy may be a therapeutic advantage over the three AIs applied in clinic. Furthermore, this new multi-target compound has the ability to sensitize the AI-resistant BC cells, which represents another advantage over the endocrine therapy used in the clinic, since resistance is a major drawback in the clinic.

Design, synthesis, biological activity evaluation and structure-activity relationships of new steroidal aromatase inhibitors. The case of C-ring and 7β substituted steroids

In this work, new steroidal aromatase inhibitors (AIs) were designed, synthesized, and tested. In one approach, C-ring substituted steroids namely those functionalized at C-11 position with an α or β hydroxyl group or with a carbonyl group as well as C-9/C-11 steroidal olefins and epoxides were studied. It was found that the carbonyl group at C-11 is more beneficial for aromatase inhibition than the hydroxyl group, and that the C-ring epoxides were more potent than the C-ring olefins, leading to the discovery of a very strong AI, compound 7, with an IC50 of 0.011 μM, better than Exemestane, the steroidal AI in clinical use, which presents an IC50 of 0.050 μM. In another approach, we explored the biological activity of A-ring C-1/C-2 steroidal olefins and epoxides in relation to aromatase inhibition and compared it with the biological activity of C-ring C-9/C-11 steroidal olefins and epoxides. On the contrary to what was observed for the C-ring olefins and epoxides, the A-ring epoxides were less potent than A-ring olefins. Finally, the effect of 7β-methyl substitution on aromatase inhibition was compared with 7α-methyl substitution, showing that 7β-methyl is better than 7α-methyl substitution. Molecular modelling studies showed that the 7β-methyl on C-7 seems to protrude into the opening to the access channel of aromatase in comparison to the 7α-methyl. This comparison led to find the best steroidal AI (12a) of this work with IC50 of 0.0058 μM. Compound 12a showed higher aromatase inhibition capacity than two of the three AIs currently in clinical use.

Ruxolitinib and exemestane for estrogen receptor positive, aromatase inhibitor resistant advanced breast cancer

Circulating IL-6, an activator of JAK/STAT signaling, is associated with poor prognosis and aromatase inhibitor (AI) resistance in hormone-receptor positive (HR+) breast cancer. Here we report the results of a phase 2 single-arm Simon 2-stage trial combining Ruxolitinib, an oral selective inhibitor of JAK1/2, with exemestane, a steroidal AI, in patients with HR+ metastatic breast cancer (MBC) after progression on non-steroidal AI (NSAI). Safety and efficacy were primary objectives, and analysis of inflammatory markers as predictors of response was a key secondary objective. Twenty-five subjects enrolled. The combination of ruxolitinib and exemestane was safe, though anemia requiring transfusion in 5/15 (33%) at the 25 mg dose in stage 1 led to a reduction to 15 mg twice daily in stage 2 (with no additional transfusions). Clinical benefit rate (CBR) in the overall study population was 24% (95% CI 9.4–45.1); 6/25 patients demonstrated stable disease for ≥6 months. Median progression-free survival was 2.8 months (95% CI 2.6–3.9). Exploratory biomarkers revealed high levels of systemic inflammation and 60% harbored a high-risk IL-6 genotype. Pharmacodynamics demonstrated modest on-target inhibition of phosphorylated-STAT3 by ruxolitinib at a tolerable dose. Thus, ruxolitinib combined with exemestane at a tolerable dose was safe but minimally active in AI-resistant tumors of patients with high levels of systemic inflammation. These findings highlight the need for more potent and specific therapies targeting inflammation in MBC.

In-Vivo Pharmacokinetics Study of Exemestane Hydrochloride Self-nanoemulsifying Drug Delivery Systems via Oral Route

Exemestane HCl (EXM) is a novel irreversible steroidal aromatase inhibitor for the adjuvant treatment of hormonally responsive breast cancer in postmenopausal women. Poor aqueous solubility of EXM is the biggest hurdle for developing solid oral dosage forms. That’s why the current study aims to evaluate the pharmacokinetics of formulating the EXM loaded self nano emulsifying drug delivery (SNEDDs) system. SNEDDs were formulated using Labrafac CC (20% w/v), Tween 80 (27%w/v), and Triacetin (54%w/v) as oil, surfactant, and co-surfactant, respectively, by water titration method. A comparative Pharmacokinetics study of EXM suspension and EXM SNEDDS was performed using a female waster rate. The developed formulation had a 37.65± 5.08 nm size and a 21.57±0.73 sec of self-emulsification time. Cmax of EXM suspension and EXM SNEDDS was found to be 122.49±8.27 and 194.86 ± 14.75 ng/mL, respectively. AUC0-720 of EMX SNEDDS was 1.71 times higher compared to EXM suspension, indicating that lipid nanoparticles improve the drug concentration in the plasma. So we conclude that SNEDDS improves the pharmacokinetic of EXM, which subsequently improves oral bioavailability.

Investigations on the in vivo metabolism of 5α-androst-2-en-17-one.

The anabolic steroid 5α-androst-2-en-17-one (2EN) is sold as a prohormone and has been investigated regarding its potential as a steroidal aromatase inhibitor. The administration of 2EN was detected in a doping control sample in 2015, and investigations into its metabolism allowed for the identification and characterization of three urinary metabolites. Unfortunately, the utility of the main metabolite 2β,3α-dihydroxy-5α-androstan-17-one for doping control purposes was hampered under routine doping control conditions due to chromatographic issues, thus warranting further studies on the metabolism of the prohibited substance. The metabolism of 2EN was reinvestigated after oral administration of twofold-deuterated 2EN employing hydrogen isotope ratio mass spectrometry (IRMS) in combination with high-accuracy/high-resolution mass spectrometry. After a single dose of 50 mg of doubly labeled 2EN, urine samples were collected for 9days. All samples were processed using routine doping control methods for IRMS analysis, and all detected metabolites were further characterized by mass spectrometry-based investigations. More than 15 different metabolites still containing the deuterium label were detected after administration. The presence of steroids exhibiting a 5β-configuration was unexpected as the administered 2EN features a 5α-configured pharmacophore. Further investigations corroborated a significant impact of the administered 2EN on etiocholanolone and 5β-androstanediol. Seven metabolites of 2EN not present as endogenous compounds were identified as potential candidates for routine doping controls and could be detected for up to 9days after administration. The new metabolites identified in this study enable the detection of the misuse of 2EN for up to 9days. The conversion of a 5α-steroid to urinary metabolites with 5β-configuration has not been reported so far and should be further investigated.

An aromatase inhibitor in combination with Zinc(II) phthalocyanine for targeted therapy of post-menopausal breast cancer

As a third-generation steroidal aromatase inhibitor, exemestane (EXE) has been clinically used for postmenopausal advanced breast cancer patients whose condition has progressed after treatment of tamoxifen. However, the further development and application of EXE was limited due to its low solubility and oral bioavailability, inevitable drug resistance and side effects. Based on the unique therapeutic advantages of photodynamic therapy (PDT), a novel aromatase-targeted photosensitizer EX-Pc was synthesized by the combination of EXE and the phthalocyanine photosensitizer. The compound EX-Pc still maintains the superior optical properties of the phthalocyanine photosensitizer upon the introduction of EXE and triethylene glycol chain. Meanwhile, the results of targeted uptake in vitro and in vivo indicated that EX-Pc exhibited high selectivity and affinity for breast cancer cells and tumor tissues, which have the overexpression of aromatase. More importantly, the compound EX-Pc exhibits significant photocytotoxicity and tumor regression ability on breast cancer cells and tumor. In addition, the compound EX-Pc shows negligible side effects and high biological safety. We believe that this is a potential strategy for the treatment of postmenopausal breast cancer.

Bone Safety Profile of Steroidal Aromatase Inhibitor in Comparison to Nonsteroidal Aromatase Inhibitors in Postmenopausal Women with Breast Cancer: A Network Meta-Analysis

Background and Objectives: Aromatase inhibitors (AIs) provide an alternative to tamoxifen as an adjuvant therapy for postmenopausal patients with breast cancer (BC). Large trials resulted better outcomes with AIs. Adjuvant therapy with AIs reduced the risk of relapse compared with tamoxifen. Systemic therapies for BC can interfere with bone turnover, either by affecting gonadal steroid hormone production or by inhibiting peripheral aromatization into estrogen. We aimed to evaluate the safety profile of bone-related events by comparing 3 AIs with tamoxifen and a placebo. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were used for network meta-analyses (NMAs). Searches were performed using PubMed, Embase/Medline, Cochrane, and Ovid databases. Randomized controlled trials comparing tamoxifen and placebo or other AIs to steroidal or nonsteroidal AIs in patients with BC reporting bone-related safety events were included in NMA. NMA in a Bayesian approach was performed using R software (ver 3.2), Gemtc package. Results: Seventeen studies reporting 4 different bone-related endpoints were included. Although there was no statistical significance, treatment with exemestane lowered the incidence of bone pain (odds ratio [OR] vs. anastrozole and letrozole: 0.63, 0.54), fracture episodes (OR vs. anastrozole and letrozole: 0.84, 0.80), and osteoporosis (OR vs. anastrozole and letrozole: 0.85, 0.73) compared with letrozole and anastrozole. Reduction in bone mineral density was lesser in exemestane than in anastrozole (mean reduction in hip: 1.05; lumbar spine: 1.25). Treatment ranking with the surface under the cumulative ranking curve showed that exemestane was found to reduce the incidence of bone-related adverse events. Conclusion: A lower incidence of bone-related safety events was observed in patients treated with exemestane.

Abstract PD5-03: Development of cardiometabolic risk factors following endocrine therapy: The pathways heart study

Abstract Purpose: Endocrine therapy is associated with cardiovascular disease among breast cancer (BC) survivors, with observed opposing effects between aromatase inhibitors (AIs) and tamoxifen. AIs deplete endogenous estrogen levels, while tamoxifen has mixed estrogenic and antiestrogenic activity. Yet, observational studies comparing AI vs. tamoxifen use may be confounded by indication and few have tested their associations with cardiometabolic risk factors. Therefore, we examined the association of AI or tamoxifen use on the incidence of newly diagnosed hypertension, diabetes, and dyslipidemia in a cohort of BC survivors within Kaiser Permanente Northern California (KPNC). Methods: The Pathways Heart Study is an ongoing cohort study within KPNC examining incident CVD outcomes and risk factors in 14,942 women with history of BC. Eligibility was: 1) stage I-IV invasive BC diagnosis between Nov 2005 and Mar 2013; 2) &amp;ge;21 years; and 3) active KPNC membership &amp;ge;12 months at diagnosis. KPNC records were used to collect demographic, socioeconomic, and health characteristics. Endocrine therapy was collected from outpatient pharmacy data. Incident hypertension, diabetes, and dyslipidemia were identified from ICD-9/10 codes, laboratory results, and/or medication use. Hazard ratios (HR) and 95% confidence intervals (CI) from Cox proportional models were used to determine whether AI and tamoxifen use were associated with incident hypertension, diabetes, and dyslipidemia compared to BC survivors not receiving either of these therapies. For each cardiometabolic risk factor, models adjusted for demographic, socioeconomic, and health characteristics and excluded women with the cardiometabolic risk factor at baseline. Results: Among 14,942 women with a history of BC, mean age at baseline was 61.2±12.8 years and mean follow-up time was 7.0±3.5 years (range 1-13.4). The frequency of use was: AI, n=6,070 (40.6%); tamoxifen, n=1,755 (11.8%); and neither, n=7,117 (47.6%). Regression models showed AI use was associated with increased risk of incident hypertension (HR: 1.1, 95% CI: 1.00-1.21) and increased risk of incident dyslipidemia (HR: 1.18, 95% CI: 1.07-1.3) relative to BC survivors who did not use endocrine therapy. (Table). In contrast, tamoxifen use was associated with decreased risk of dyslipidemia (HR: 0.8, 95% CI: 0.68-0.94) relative to BC survivors who did not use endocrine therapy. Neither AI nor tamoxifen use was associated with risk of incident diabetes. Conclusion: Compared to BC survivors who did not use endocrine therapy, women treated with AIs had a higher risk of incident hypertension and dyslipidemia, while women treated with tamoxifen had a lower risk of dyslipidemia. AIs reduce endogenous estrogen levels, which can alter lipid profiles, although prior studies have been inconsistent, possibly due to differences in steroidal and non-steroidal AIs. More work is needed to understand the implications of these associations on long-term cardiovascular health and how to best manage cardiometabolic risk factors in BC survivors with a history of endocrine therapy use. Table. Adjusted1 hazard ratios (95% confidence intervals) of incident cardiometabolic risk factors among women with a history of breast cancer, by endocrine therapy useNo Endocrine Therapy(n=7,117)Endocrine TherapyAromatase inhibitor(n=6,070)Tamoxifen(n=1,755)Incident HypertensionRef1.10 (1.00, 1.21)0.98 (0.85, 1.14)Incident DiabetesRef0.99 (0.87, 1.13)0.98 (0.80, 1.20)Incident DyslipidemiaRef1.18 (1.07, 1.30)0.80 (0.68, 0.94)1Adjusted for age, race/ethnicity, baseline body mass index, AJCC stage, menopausal status, smoking status, education level, income, chemotherapy, radiation therapy, and prevalent cardiovascular disease. Citation Format: Heather Greenlee, Eileen Rillamas-Sun, Carlos Iribarren, Richard Cheng, Romain Neugebauer, Jamal S. Rana, Mai Nguyen-Huynh, Zaixing Shi, Cecile A. Laurent, Valerie S. Lee, Janise M. Roh, Hanjie Shen, Dawn L. Hershman, Lawrence H. Kushi, Marilyn L. Kwan. Development of cardiometabolic risk factors following endocrine therapy: The pathways heart study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD5-03.

The Roles of Aromatase Inhibitors in Treating Hypogonadism and Male Infertility

Testis is an organ with both endocrine and exocrine functions. The former stands for testosterone release, and the latter represents sperm production. Spermatogenesis is a process highly depending on adequate supply of testosterone by the Leydig cells of the testis. In men at the reproductive age, more than 90% of testosterone produced is used for spermatogenesis. In men with diminished testosterone secretion in testis, or hypogonadism, the spermatogenesis process is impaired. Testosterone can be converted into estradiol through the catalyzation of aromatase, a cytochrome P450 enzyme presented in the peripheral tissue. Blocking the activity of aromatase causes an elevation of serum testosterone and a decrease of serum estradiol levels. These effects result in an increase of testosterone-to-estradiol ratio. Infertile males with dysfunction of spermatogenesis may demonstrate a low testosterone-to-estradiol ratio. Studies have shown that aromatase inhibitors (AIs) are beneficial to treat patients with impaired spermatogenesis, by demonstrating improvement of the semen parameters in men with oligoasthenoteratozoospermia. Besides, AIs can also be applied in other health issues, such as hypogonadism-related erectile dysfunction, short statue, depression, or male breast cancer. There are two different types of AIs: steroidal and nonsteroidal. Steroidal AI (e.g., testolactone) is an irreversible, but weaker inhibitors, while nonsteroidal AIs (e.g., letrozole and anastozole) are potent reversible inhibitors. Both types of AIs demonstrate plausible effects to improve semen parameters. In this review, the physiological action of aromatase and the indications of AIs treatment are discussed in detail, especially focusing on the function of spermatogenesis in infertile men.

Lack of cross-resistance between non-steroidal and steroidal aromatase inhibitors in breast cancer patients: the potential role of the adipokine leptin

PurposeThe aromatase inactivator exemestane may cause clinical disease stabilization following progression on non-steroidal aromatase inhibitors like letrozole in patients with metastatic breast cancer, indicating that additional therapeutic effects, not necessarily related to estrogen-suppression, may be involved in this well-known “lack of cross-resistance”.MethodsPostmenopausal women with ER positive, HER-2 negative, locally advanced breast cancer were enrolled in the NEOLETEXE-trial and randomized to sequential treatment starting with either letrozole (2.5 mg o.d.) or exemestane (25 mg o.d.) followed by the alternative aromatase inhibitor. Serum levels of 54 cytokines, including 12 adipokines were assessed using Luminex xMAP technology (multiple ELISA).ResultsSerum levels of leptin were significantly decreased during treatment with exemestane (p < 0.001), regardless whether exemestane was given as first or second neoadjuvant therapy. In contrast, letrozole caused a non-significant increase in serum leptin levels in vivo.ConclusionsOur findings suggest an additional and direct effect of exemestane on CYP-19 (aromatase) synthesis presumably due to effects on the CYP19 promoter use that is not present during therapy with the non-steroidal aromatase inhibitor letrozole. Our findings provide new insights into the influence of clinically important aromatase inhibitors on cytokine levels in vivo that contribute to the understanding of the clinically observed lack of cross-resistance between non-steroidal and steroidal aromatase inhibitors in breast cancer patients.Trial registrationRegistered on March 23rd 2015 in the National trial database of Norway (Registration number: REK-SØ-84-2015).

Effects of PI3K inhibition in AI-resistant breast cancer cell lines: autophagy, apoptosis, and cell cycle progression.

Breast cancer is the leading cause of cancer death in women. The aromatase inhibitors (AIs), Anastrozole (Ana), Letrozole (Let), and Exemestane (Exe) are a first-line treatment option for estrogen receptor-positive (ER+) breast tumors, in postmenopausal women. Nevertheless, the development of acquired resistance to this therapy is a major drawback. The involvement of PI3K in resistance, through activation of the PI3K/AKT/mTOR survival pathway or through a cytoprotective autophagic process, is widely described. The involvement of autophagy in response to Ana and Let treatments and the effects of the combination of BYL-719, a PI3K inhibitor, with AIs were explored in AI-resistant breast cancer cell lines (LTEDaro, AnaR, LetR, and ExeR). We demonstrate that Ana and Let treatments do not promote autophagy in resistant breast cancer cells, contrary to Exe. Moreover, the combinations of BYL-719 with AIs decrease cell viability by different mechanisms by nonsteroidal vs. steroidal AIs. The combination of BYL-719 with Ana or Let induced cell cycle arrest while the combination with Exe promoted cell cycle arrest and apoptosis. In addition, BYL-719 decreased AnaR, LetR, and ExeR cell viability in a dose- and time-dependent manner, being more effective in the ExeR cell line. This decrease was further exacerbated by ICI 182,780. These results corroborate the lack of cross-resistance between AIs verified in the clinic, excluding autophagy as a mechanism of resistance to Ana or Let and supporting the ongoing clinical trials combining BYL-719 with AIs.

Synthesis, Aromatase Inhibitory, Antiproliferative and Molecular Modeling Studies of Functionally Diverse D-Ring Pregnenolone Pyrazoles

Aromatase, a cytochrome P450 hemoprotein that is responsible for estrogen biosynthesis by conversion of androgens into estrogens, has been an attractive target in the treatment of hormonedependent breast cancer. Design of new steroidal aromatase inhibitors becomes imperative. Synthesis and biological evaluation of two classes of structurally and functionally diverse D-ring pregnenolone pyrazoles as type I aromatase inhibitors and antiproliferative agents. Pregnenolone (1) was converted to 3β-hydroxy-21-hydroxymethylidenepregn-5-en-20-one (2), which upon cyclization with phenylhydrazine generated regioisomeric pairs of pyrazoles 4 and 5. Further, Knoevenagel condensation of pregnenolone (1) with 3-oxo-3-phenylpropanenitrile (6) produced 2-benzoyl-3-(3b-hydroxyandrostan- 5-ene-20-ylidene)-but-2-enenitrile (7), which upon cyclization with hydrazine or phenylhydrazine generated the pyrazoles 8 and 9. All new steroidal derivatives were tested for their aromatase inhibition activity using Dibenzylfluorescein (DBF) based fluorescence assay developed by Stresser et al. Antiproliferative activities were measured using Sulforhodamine B assay. The activities were promising and there was a coherence between aromatase inhibitory and antiproliferative activities. The study reveals the immense potential of pregnenolone pyrazoles as aromatase inhibitors for the treatment of breast cancer. Molecular docking studies proved efficient binding of the new steroidal analogs on human placental aromatase. In the overall study, most of the compounds exhibited potential activity for the treatment of hormone dependent breast cancer. Compounds 4c and 4d were found to be the most promising pharmacons. Furthermore, compounds 4c and 4d were applied for their molecular docking study on human placental aromatase to predict their possible binding modes with the enzyme. These studies revealed that such molecules have high scope and potential for further investigation towards the treatment of estrogen dependent breast cancer.

Insights on the interaction mechanism of exemestane to three digestive enzymes by multi-spectroscopy and molecular docking

Exemestane is an irreversible steroidal aromatase inhibitor, typically used to treat breast cancer. As an anti-tumor drug, exemestane has more obvious side effects on the gastrointestinal tract. The purpose of this work is to investigate the combination of exemestane with three important digestive enzymes including pepsin (Pep), trypsin (Try) and α-Chymotrypsin (α-ChT) so as to analyze the mechanism of the gastrointestinal adverse effects causing by exemestane binding. Enzyme activity experiment showed that the enzyme activity of Pep was decreased in the presence of exemestane. Fluorescence spectra revealed that exemestane formed stable complexes with digestive enzymes, and the quenching mechanism of drug-digestive enzymes interaction were all static quenching. The binding constants of Pep, Try and α-ChT at 298 K were 2.34 × 105, 1.45 × 105, and 2.05 × 105 M−1, respectively. Synchronous fluorescence and 3D fluorescence spectroscopy showed that the conformation of exemestane was slightly changed after combining with digestive enzymes, and non-radiative energy transfer occurred. Circular dichroism results indicated that exemestane could change the secondary structure of digestive enzymes via increase the α-helix content and decrease in the β-sheet content. Thermodynamic parameters (ΔH0, ΔS0, and ΔG0) revealed that exemestane interacted with α-ChT through electrostatic force, and the binding force with Pep and Try was van der Waals interactions and hydrogen, which was basically consistent with the molecular docking results.

Abstract CT028: A pilot study of pembrolizumab and exemestane/leuprolide in premenopausal hormone receptor positive/HER2 negative locally advanced or metastatic breast cancer (PEER)

Abstract Interim Analysis Background: Despite the success of immunotherapy in triple negative breast cancer, no approved immunotherapy is available for HR+, HER2- MBC patients. Among HR+/HER2- patients(pts), luminal subtype B pts who are more resistant to endocrine therapy, demonstrate higher tumor infiltrating lymphocytes, higher immune score, and higher expression of PD-L1 than luminal subtype A pts. In addition, estrogen is known to result in immunosuppressive microenvironment. Exemestane, as a steroidal aromatase inhibitor, provides less than 10% overall response rate in second or third line of endocrine therapy for MBC pts. This pilot study aims to observe the efficacy of a combination of exemestane, leuprolide, and pembrolizumab in pre-/perimenopausal HR+, HER2- locally advanced or MBC pts who failed front-line endocrine therapy. Methods: This single-center, nonrandomized, open-label, phase Ib/II study of exemestane/leuprolide plus pembrolizumab enrolled a cohort of endocrine resistant HR+, HER2-, pre-/perimenopausal, locally advanced or MBC pts who 1) had failed adjuvant endocrine therapy within 12 months, 2) had failed at least 2 lines of prior endocrine therapy for MBC, 3) had failed 1st line endocrine therapy within 6 months or 1st line endocrine therapy+ CDK4, 6 inhibitor within 12 months. No prior chemotherapy for locally advanced or MBC was allowed. Patients received 25mg exemestane orally daily, 3.6mg leuprolide subcutaneous injection every 28 days, and pembrolizumab 150mg IV on day 1/day 15 every 28 days. Primary objective was to estimate the efficacy of the exemestane, leuprolide plus pembrolizumab combination defined by progression-free survival (PFS) rate at 8 months. Secondary objectives included safety, objective response rate (ORR), clinical benefit rate (CBR), and PFS. Results: Of 14 pts enrolled, 6 (42.9%) received 1 line and 8 (57.1%) received 2 lines of prior endocrine therapy in the locally advanced/metastatic setting. Safety of the combination was generally consistent with known side effects of exemestane, leuprolide, and pembrolizumab and was generally manageable. Grade 3/4 adverse events in ≥1 pt included AST increase (4 pts/28.6%), ALT increase (4 pts/28.6), and hypo/hyperthyroidism (1 pt, 7.1%). Nine pts did not progress or die at 8 months (64.3% PFS rate at 8th month). In the 13 evaluable pts, 5 had confirmed partial response [PR] (ORR=38.4%), 6 had confirmed stable disease[SD, 46.2%]. The disease control rate (complete response [CR]+partial response [PR]+stable disease [SD]) was 84.6%. CBR (CR+PR+SD persisting for ≥6 months) was 76.9%. Median PFS of the evaluable pts, PR pts, SD pts, and PD pts were 10.2 months, 15.8months, 10.1 months, and 2.4 months respectively. Conclusions: Combination of exemestane, leuprolide plus pembrolizumab demonstrated a generally tolerable safety profile with numerically higher rate of transaminase elevations than reported for the individual treatments. Compared to historical data for exemestane/leuprolide or for pembrolizumab monotherapy in a similar pt population, a meaningful higher ORR and longer PFS were observed. Citation Format: I-Chun Chen, Ching-Hung Lin, Dwan-Ying Chang, Tom Wei-Wu Chen, Ming-Yang Wang, Wei-Li Ma, Yi-Ting Lin, Shu-Min Huang, Yen-Shen Lu. A pilot study of pembrolizumab and exemestane/leuprolide in premenopausal hormone receptor positive/HER2 negative locally advanced or metastatic breast cancer (PEER) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT028.

Bone safety profile of steroidal aromatase inhibitor in comparison to non-steroidal aromatase inhibitors in postmenopausal women with breast cancer: A network meta-analysis.

527 Background: Steroidal and non-steroidal aromatase inhibitors (AIs) provide better therapeutic response in comparison to other endocrine therapies in the adjuvant treatment of breast cancer (BC). They interfere with bone turnover which may lead to increased incidence of bone related safety events. There are no head-on studies comparing the incidence of bone safety events and hence we performed this network meta-analysis (NMA) to compare the incidence of bone safety events among patients treated with steroidal and non-steroidal AIs. Methods: Literature searches were performed in PubMed and Embase with key words to identify randomized controlled trials in BC patients treated with AIs in adjuvant settings compared against tamoxifen or other AIs, reporting any bone-related safety events. The study was designed as per PRISMA guidelines; publication bias was evaluated by comparison-adjusted funnel plots. Bayesian NMA was done by R software (ver 3.2), GemtC package. Odds ratio (OR) and the surface under the cumulative ranking curve (SUCRA) values were used to interpret the results. Results: 15 studies reporting 6 different bone-related endpoints were included. Treatment with steroidal AI, exemestane led to lower incidence of bone pain (OR Vs anastrozole and letrozole: 0.59, p=0.63; 0.54, p=0.75), fracture episodes (OR Vs anastrozole and letrozole: 0.84, p=0.41; 0.85, p=0.73), joint stiffness (OR Vs anastrozole: 0.55, p=0.73) and osteoporosis (OR Vs anastrozole and letrozole: 0.86, p=0.41; 0.74, p=0.29) (Table) in comparison to letrozole and anastrozole. Reduction in bone mineral density was also lesser in exemestane than anastrozole (mean reduction in hip: 1.08; lumbar spine: 1.34). SUCRA values suggested exemestane to be the drug with maximum likelihood for reducing the incidence of bone-related adverse events. Conclusions: This NMA suggested that bone-related safety events might be lower in early BC patients treated with exemestane in comparison to non-steroidal AIs, anastrozole and letrozole. Although there was no statistical significance, further head-on studies are required to substantiate our results.[Table: see text]

A novel electrochemical sensor based on functionalized glassy carbon microparticles@CeO2 core–shell for ultrasensitive detection of breast anticancer drug exemestane in patient plasma and pharmaceutical dosage form

A novel core–shell structure composed of functionalized glassy carbon microspheres (f-GC) as core and CeO2 nanoparticles as shell was successfully synthesized by using hydrothermal process (H). The morphology and composition of the as-prepared f-GC@CeO2-H core–shell microspheres were characterized using XRD, SEM, TEM, EDX and mapping analysis. Electrochemical investigations revealed that f-GC@CeO2-H modified carbon rod electrode (CRE) possessed intriguing properties towards electrosensing breast anticancer exemestane (EXE) due to the synergistic interactions between f-GC core and CeO2 nanoparticles shell. The newly sensor f-GC@CeO2-H/CRE exhibited a high electrocatalytic activity towards electro-reduction of EXE and under the optimal conditions, the linear range of EXE was 0.05 µM to 10.9 µM with a low limit of detection of 18 nM. Furthermore, electrosensing of the steroidal aromatase inhibitor EXE in the presence of the non-steroidal aromatase inhibitor letrozole (LTZ) was achieved without anti-interference ability. The developed sensor shows admirable sensitivity in the detection of the two aromatase inhibitors simultaneously in biologically relevant samples. Finally, the proposed sensor was very effective for EXE determination from commercial tablets, human fluids and clinical patient blood.

Abstract GS4-02: E2112: Randomized phase 3 trial of endocrine therapy plus entinostat/placebo in patients with hormone receptor-positive advanced breast cancer. A trial of the ECOG-ACRIN cancer research group

Abstract Background: Endocrine therapy resistance in advanced breast cancer remains a significant clinical problem that may be overcome with use of histone deacetylase (HDAC) inhibitors such as entinostat. The ENCORE 301 randomized phase II study reported an improvement in progression-free (PFS) and overall survival (OS) with the addition of entinostat to the steroidal aromatase inhibitor (AI) exemestane in patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer. Protein lysine acetylation in peripheral blood mononuclear cells (PBMCs) was associated with prolonged PFS in the entinostat arm. Methods: E2112 is a multicenter randomized double-blind, placebo-controlled phase III study that enrolled men or women with advanced HR-positive, HER2-negative breast cancer whose disease had progressed on a non-steroidal AI in the adjuvant or metastatic setting (NCT02115282). Study participants were also required to have an ECOG performance status 0-1 with measurable or non-measurable (limited to 20% of the study population) disease. One prior chemotherapy for metastatic disease and prior treatment with fulvestrant and a CDK4/6 inhibitor was permitted but not required. Participants received exemestane 25mg po daily and entinostat (EE)/placebo (EP) 5mg po every week. Primary endpoints were PFS (central review) and OS. One-sided type 1 error 0.025 was split between two hypothesis tests: 0.001 for PFS test and 0.024 for OS. PFS tested in the first 360 pts, 88.5% power to detect 42% reduction in the hazard of PFS failure (median PFS, 4.1 to 7.1 months); OS tested in all 600 pts, 80% power to detect 25% reduction in the hazard of death (median OS, 22 to 29.3 months). Secondary endpoints included safety, objective response rate (ORR), and changes in protein lysine acetylation status in PBMCs (CD3+ T cells, CD14+ monocytes, CD19+ B cells, pan-leukocyte marker CD45+ cells, CD56+ NK cells) between C1D1 and C1D15 (integrated biomarker). Results: A total of 608 participants were randomized between March 2014 and October 2018 (305 EE, 303 EP), 98% enrolled in USA. Characteristics were well balanced between the arms. Median age was 63 years (range, 29-91), 99% female, 95% postmenopausal, 80% white and 15% black. A majority (84%) had disease resistant to AI in the metastatic setting at study entry, 78% had measurable disease and 60% visceral disease. Prior treatments included chemotherapy (60%), fulvestrant (30%), CDK4/6 inhibitor (35%), everolimus (3%). Median prior lines of chemotherapy was 1 (range, 0-4) and endocrine therapy was 2 (range, 1-7); in adjuvant/metastatic setting. Grade 3/4 adverse events in EE arm included neutrophil count decreased (20%), hypophosphatemia (14%), anemia (8%), white blood cell decreased (6%), fatigue (4%), diarrhea (4%), and platelet count decreased (3%). At final analysis, median PFS was 3.3 months (EE) versus 3.1 months (EP) (HR=0.87, 95% CI: 0.67, 1.13, p=0.30). Median OS was 23.4 months (EE) versus 21.7 months (EP) (HR=0.99, 95% CI: 0.82, 1.21, p=0.94). ORR was 4.6% (EE) and 4.3% (EP). The median fold change in lysine acetylation in PBMCs was approximately 1.5 in EE arm, and 1 in EP arm. Participants on EE had significantly higher increase in lysine acetylation by C1D15 than patients on EP (397 paired samples available for analysis, p&amp;lt;0.001 for all). Additional biomarker analyses will be presented at time of meeting. Conclusion: The combination of exemestane and entinostat did not improve survival in AI resistant advanced HR-positive, HER2-negative breast cancer. Pharmacodynamic analysis confirmed target inhibition in entinostat-treated patients. Citation Format: Roisin M Connolly, Fengmin Zhao, Kathy D Miller, Min-Jung Lee, Richard L Piekarz, Karen L Smith, Ursa Brown-Glaberman, Jennifer S Winn, Bryan A Faller, Adedayo A Onitilo, Mark E Burkard, George T Budd, Ellis G Levine, Melanie E Royce, Peter A Kaufman, Alexandra Thomas, Jane B Trepel, Antonio C Wolff, Joseph A Sparano. E2112: Randomized phase 3 trial of endocrine therapy plus entinostat/placebo in patients with hormone receptor-positive advanced breast cancer. A trial of the ECOG-ACRIN cancer research group [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS4-02.