Innovation has frequently been described as the key to drug discovery. However, in the daily routine, medicinal chemists often tend to stick to the functional groups and structural elements they know and love. Blockbuster cancer drug Velcade (bortezomib), for example, was rejected by more than 50 companies, supposedly because of its unusual boronic acid function (as often repeated: "only a moron would put boron in a drug!"). Similarly, in the discovery process of the pan-CDK inhibitor BAY 1000394, the unconventional proposal to introduce a sulfoximine group into the lead series also led to sneers and raised eyebrows, since sulfoximines have seldom been used in medicinal chemistry. However, it was the introduction of the sulfoximine group that finally allowed the fundamental issues of the project to be overcome, culminating in the identification of the clinical sulfoximine pan-CDK inhibitor BAY 1000394. This Minireview provides an overview of a widely neglected opportunity in medicinal chemistry--the sulfoximine group.

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The DNA damage response (DDR) secures the integrity of the genome of eukaryotic cells. DDR deficiencies can promote tumorigenesis but concurrently may increase dependence on alternative repair pathways. The ataxia telangiectasia and Rad3-related (ATR) kinase plays a central role in the DDR by activating essential signaling pathways of DNA damage repair. Here, we studied the effect of the novel selective ATR kinase inhibitor BAY 1895344 on tumor cell growth and viability. Potent antiproliferative activity was demonstrated in a broad spectrum of human tumor cell lines. BAY 1895344 exhibited strong monotherapy efficacy in cancer xenograft models that carry DNA damage repair deficiencies. The combination of BAY 1895344 with DNA damage-inducing chemotherapy or external beam radiotherapy (EBRT) showed synergistic antitumor activity. Combination treatment with BAY 1895344 and DDR inhibitors achieved strong synergistic antiproliferative activity in vitro, and combined inhibition of ATR and PARP signaling using olaparib demonstrated synergistic antitumor activity in vivo. Furthermore, the combination of BAY 1895344 with the novel, nonsteroidal androgen receptor antagonist darolutamide resulted in significantly improved antitumor efficacy compared with respective singleagent treatments in hormone-dependent prostate cancer, and addition of EBRT resulted in even further enhanced antitumor efficacy. Thus, the ATR inhibitor BAY 1895344 may provide new therapeutic options for the treatment of cancers with certain DDR deficiencies in monotherapy and in combination with DNA damage-inducing or DNA repair-compromising cancer therapies by improving their efficacy.

Selective inhibition of exclusively transcription‐regulating PTEFb/CDK9 is a promising new approach in cancer therapy. Starting from lead compound BAY‐958, lead optimization efforts strictly focusing on kinase selectivity, physicochemical and DMPK properties finally led to the identification of the orally available clinical candidate atuveciclib (BAY 1143572). Structurally characterized by an unusual benzyl sulfoximine group, BAY 1143572 exhibited the best overall profile in vitro and in vivo, including high efficacy and good tolerability in xenograft models in mice and rats. BAY 1143572 is the first potent and highly selective PTEFb/CDK9 inhibitor to enter clinical trials for the treatment of cancer.

Neglected sulfur(VI) pharmacophores in drug discovery: exploration of novel chemical space by the interplay of drug design and method development † U. LückingHistorically, sulfoximines, sulfondiimines and sulfonimidamides have been neglected pharmacophores in drug discovery even though they offer very interesting properties. This highlight shares the key learnings of various lead optimization approaches at Bayer AG that have successfully utilized these neglected sulfur(VI) functional groups to deliver multiple clinical candidates. In this context, the key synthetic methods utilized for the synthetic preparation of these unusual compounds will be outlined.Scheme 1 General structures of sulfones 1, sulfonamides 2, and aza analogues sulfoximines 3, sulfondiimines 4 and sulfonimidamides 5. Scheme 2 Structures and key properties of the pan-CDK inhibitors ZK 304709, sulfoximine model compound 6 and roniciclib. † Dedicated to Professor Julius Rebek on the occasion of his 75th birthday. Scheme 12 One-pot synthesis of NH sulfonimidamides 5 by NH transfer to sulfinamides 17. Scheme 13 N-Functionalization of NH sulfonimidamide model compound 5a.