Min S. Lee

Background: Dimethandrolone undecanoate (DMAU) is under development as a single agent hormonal male contraceptive. DMAU is a prodrug hydrolyzed by esterase(s) to the active metabolite dimethandrolone (DMA) which has dual androgenic and progestogenic actions. Phase 1 clinical trial results show DMAU to be well‐tolerated as an oral contraceptive in healthy men; however, delivery of DMAU as a long‐acting injectable rather than a daily oral formulation would provide user compliance benefits and address oral bioavailability concerns. Objective: To assess the safety, pharmacokinetics (PK), and long‐acting contraceptive potential of DMAU in male non‐human primates (NHP) when delivered as an injectable or oral formulation. Materials and methods: DMAU was administered to cynomolgus macaques orally for 9 months or as five weekly intramuscular (IM) injections and to rhesus macaques as a single IM injection. Evaluations of safety, fertility indicators, and serum levels of DMAU and DMA were followed > 2 years post‐dose. Results: Repeat dose oral and IM administrations were well‐tolerated with no significant toxicological findings. Dramatic reductions in serum testosterone concentration occurred within days of administration followed by sustained suppression of additional fertility indicators (e.g., serum inhibin B, sperm count, and testicular spermatogenesis). Slight body weight increases and reductions in testes weight also occurred. Repeat DMAU injections resulted in DMA serum concentrations above the lower limit of quantification (1 ng/mL) for > 500 days. DMAU PK parameters increased with increasing IM dose, while dose dependence was not seen for serum DMA concentrations suggesting a depot effect with a reservoir of non‐circulating prodrug remaining at the injection site which gets slowly hydrolyzed to DMA and absorbed into circulation. Testosterone levels and spermatogenesis returned by the end of the recovery period. Conclusions: Nonclinical safety, PK, and pharmacodynamic data in male NHP demonstrate the safe, well‐tolerated, long‐acting, and reversible contraceptive potential of injectable DMAU.

11β-Methyl-19-nortestosterone dodecylcarbonate (11β-MNTDC) is a prodrug of 11β-MNT and is being considered as a promising male oral contraceptive candidate in clinical development. However, the oral administration of 11β-MNTDC exhibits an ~200-fold lower serum concentration of 11β-MNT compared to 11β-MNTDC, resulting in the poor bioavailability of 11β-MNT. To elucidate the role of the first-pass metabolism of 11β-MNT in its poor bioavailability, we determined the biotransformation products of 11β-MNT and its prodrugs in human in vitro models. 11β-MNT and its two prodrugs 11β-MNTDC and 11β-MNT undecanoate (11β-MNTU) were incubated in cryopreserved human hepatocytes (HHs) and subjected to liquid chromatography–high resolution tandem mass spectrometry analysis, which identified ten 11β-MNT biotransformation products with dehydrogenated and glucuronidation (11β-MNTG) metabolites being the major metabolites. However, 11β-MNTG formation is highly variable and prevalent in human intestinal S9 fractions. A reaction phenotyping study of 11β-MNT using thirteen recombinant UDP-glucuronosyltransferase (UGT) enzymes confirmed the major role of UGT2B17 in 11β-MNTG formation. This was further supported by a strong correlation (R² > 0.78) between 11β-MNTG and UGT2B17 abundance in human intestinal microsomes, human liver microsomes, and HH systems. These results suggest that 11β-MNT and its prodrugs are rapidly metabolized to 11β-MNTG by the highly polymorphic intestinal UGT2B17, which may explain the poor and variable bioavailability of the drug.

Background: Current options for male contraception are limited to condoms, the withdrawal method, or a vasectomy. Studies indicate that men have expressed growing interest in bearing responsibility for family planning.Objectives: To review prior studies investigating the role of an androgen‐only or androgen with progestin regimen for hormonal male contraception and to provide an update of a promising new hormonal agent, a transdermal gel.Discussion: Thus far, there have been six studies conducted in couples evaluating the contraceptive efficacy of an androgen‐only or androgen co‐administered with a progestin regimen for hormonal male contraception. The only ongoing study is by the National Institute of Child Health and Human Development, in collaboration with the Population Council. They have developed a novel transdermal gel containing testosterone and segesterone acetate (Nestorone), a progestin. An ongoing phase II study enrolling more than 460 couples has shown great potential with respect to the product's efficacy, safety, reversibility, and acceptability. As this agent advances in development, a rapid at‐home test for sperm concentration will provide couples with immediate feedback regarding their potential for pregnancy.Conclusion: There is promise for the first‐of‐its‐kind hormonal male contraceptive, a transdermal gel, to achieve market approval for distribution in the United States and elsewhere. Its safety, efficacy, reversibility, and user‐control are all appealing qualities that make it readily adoptable for clinical practice.

Male contraceptive development has included use of testosterone (T) with or without a progestin or the use of a single molecule such as progestogenic androgens (PA) for suppression of testicular T production. Expanding upon the vast amount of data accumulated from nortestosterone (NT), NT analogs, and their prodrugs, a new series of PA, the C7 methyl, and ethyl α-substituted T analogs 7α-Methyltestosterone (7α-MT) and 7α-Ethyltestosterone (7α-ET), respectively, were hypothesized and designed to have superior androgenic and progestogenic activities when compared with parent T. Results from androgen receptor and progesterone receptor competitive binding and transcriptional activation assays showed favorable activities for these T analogs. Additionally, 7α-MT and 7α-ET were shown to be active substrates for aromatase in vitro, mitigating a potential negative impact on bone mineral density with long-term use. In conjunction with this observation, the diminished metabolism of these T analogs by 5α-reductase may reduce potential concerns for prostatic growth. In the Hershberger in vivo rat bioassay, 7α-MT and 7α-ET showed superior androgenic and anabolic activities as compared with T. These C7 α-substituted T analogs also showed clear progestogenic activity in the McPhail bioassay which evaluated endometrial glandular arborization in a rabbit model. The discovery of aromatizable molecules with reduced metabolism by 5α-reductase that have androgenic, anabolic, and progestogenic properties indicates that the core and/or prodrugs of 7α-MT and 7α-ET are promising molecules for further development as male contraceptive PAs.

The long and challenging drug development process begins with discovery biology for the selection of an appropriate target for a specific indication. Target is a broad term that can be applied to a range of biological entities such as proteins, genes, and ribonucleic acids (RNAs). Although there are numerous databases available for mining biological entities, publicly available searchable, downloadable databases to aid in target selection for a specific disease or indication (e.g., developing contraceptives and infertility treatments) are limited. We report the development of the Contraceptive and Infertility Target DataBase (https://www.citdbase.org), which provides investigators an interface to mine existing transcriptomic and proteomic resources to identify high-quality contraceptive/infertility targets. The development of similar databases is applicable to the identification of targets for other diseases and conditions.