Pharmacological characterization of A-131701, a novel α1-adrenoceptor antagonist selective for α(1A)- and α(1D)-compared to α(1B)-adrenoceptors

Arthur A. Hancock*, Steven A. Buckner, Michael E. Brune, Sweta Katwala, Ivan Milicic, Lynne M. Ireland, Patricia A. Morse, Sheila M. Knepper, Michael D. Meyer, Christopher R. Chapple, Russell Chess-Williams, Amanda J. Noble, Michael Williams, James F. Kerwin

*Corresponding author for this work

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New compounds selective for α(1A)-adrenoceptors in the prostate may offer enhanced efficacy for benign prostatic hyperplasia (BPH), with fewer side effects than current treatment. A-131701 (3-[2-((3aR,9bR)-cis-6-methoxy- 2,3,3a,4,5,9b,hexahydro-[1H]-benz[e]isoindol-2- yl)ethyl]pyridol]3',4':4,5]thieno [3,2-d]pyrimidine-2,4(1H,3H)-dione), from a novel class of benz[e]isolindole pyridothienopyrimidines and pyridothienopyrazines, is selective for α(1a)- and α(1d)-adrenoceptors in radioligand binding studies (0.22 nM at α(1a)-, 0.97 nM at α(1d))- compared to α(1b)-sites (2.5 nM) and in isolated tissue bioassays (pA2 values of 8.9-9.0 for α(1A)-receptors in rat vas deferens or canine prostate strips, 9.1 at α(1D)-sites (rat aorta)), compared to 7.9 at α(1B)-sites (rat spleen). A-131701 also potently blocked radioligand binding to α1- adrenoceptors in canine and human prostatic membranes, but was considerably weaker at α2-adrenoceptors. In isoflurane-anesthetized dogs, A-131701 antagonized epinephrine-induced increases in intraurethral pressure (IUP) with a pseudo-pA2 value of 8.17. In spontaneously hypertensive rats. A- 131701 caused transient decreases in mean arterial blood pressure (MABP) and transient tachycardia. The area under curve (AUC060 min for the hypotensive response was dose-related, with long index value A-131701 of 5.33, suggesting a selectivity of >600-fold comparing IUP to MABP effects. In pentobarbital-anesthetized dogs, A-131701 was more potent in blocking phenylephrine (PHE)-induced increases in IUP (pseudo-pA2 = 8.0), compared to concurrently measured MABP (pseudo-pA2 = 7.2), or sixfold selective. Doses greater than 1,000 nmol/kg i.v. of A-131701 were required to lower blood pressure by 10 mm Hg in these dogs (pED10 = 5.57), indicating a uroselectivity ratio of >250, superior to doxazosin, terazosin, or tamsulosin. Thus, A-131701 is selective for α(1A)- and α(1D)- vs. α(1B)- adrenoceptors in vitro, and prostatic function vs. blood pressure effects in vivo, which may provide therapeutic advantages in the treatment of BPH.

Original languageEnglish
Pages (from-to)140-162
Number of pages23
JournalDrug Development Research
Issue number4
Publication statusPublished - 1 Aug 1998
Externally publishedYes

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    Hancock, A. A., Buckner, S. A., Brune, M. E., Katwala, S., Milicic, I., Ireland, L. M., Morse, P. A., Knepper, S. M., Meyer, M. D., Chapple, C. R., Chess-Williams, R., Noble, A. J., Williams, M., & Kerwin, J. F. (1998). Pharmacological characterization of A-131701, a novel α1-adrenoceptor antagonist selective for α(1A)- and α(1D)-compared to α(1B)-adrenoceptors. Drug Development Research, 44(4), 140-162.<140::AID-DDR2>3.0.CO;2-R