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Palbociclib, ribociclib, and abemaciclib are inhibitors of the cyclin-dependent kinases 4 and 6 approved for the treatment of locally advanced or metastatic breast cancer. In this review, we provide an overview of the available clinical pharmacokinetic and pharmacodynamic characteristics of these novel drugs, summarize the results of food-effect and drug-drug interaction studies, and highlight exposure-response and exposure-toxicity relationships. All three drugs exhibit a large inter-individual variability in exposure (coefficient of variation range 40-95% for minimum plasma concentration), are extensively metabolized by cytochrome P450 3A4, and have their brain penetration limited by efflux transporters. Abemaciclib has three active metabolites with similar potency that are clinically relevant (i.e., M2, M20, M18), whereas the metabolites of palbociclib and ribociclib are not of clinical significance. Pharmacokinetic exposure increases in a dose-proportional manner for palbociclib, whereas exposure increases under- and over-proportionally with an increasing dose for abemaciclib and ribociclib, respectively. High exposure is associated with an increased risk of neutropenia, and for ribociclib also to corrected QT prolongation. For abemaciclib, a clear exposure-efficacy relationship has been described, while for palbociclib and ribociclib exposure-response analyses remain inconclusive. Future studies are needed to address exposure-efficacy relationships to further improve dosing.

A model for the homeostasis of glucose through the regulating hormones glucagon and insulin is described. It contains a subsystem that models the internalization of the glucagon receptor. Internalization is a mechanism in cell signaling, through which G-protein coupled receptors are taken from the surface of the cell to the endosome. The model is used to interpret data from a glucagon challenge test in which subjects have been under treatment with a novel glucagon receptor anti-sense drug which is aimed at reducing the number of receptors in the liver. It is shown how the receptor internalization results in tolerance of the blood glucose concentration to glucagon-induced hyperglycemia. We quantify the reduction of the number of receptors using the model and the data before and after treatment. Electronic supplementary material The online version of this article (doi:10.1007/s10928-019-09655-2) contains supplementary material, which is available to authorized users.

ISIS 388626 is an antisense sodium-glucose cotransporter 2 (SGLT2) inhibitor designed to treat type 2 diabetes mellitus by induction of glucosuria. ISIS 388626 was demonstrated to be safe and effective in preclinical trails in several species. We undertook the present study to evaluate the safety and efficacy of 13 weekly doses of 50, 100, and 200 mg of ISIS 388626 in humans. ISIS 388626 increased 24-hour urinary glucose excretion dose dependently with 508.9 ± 781.45 mg/day in the 100-mg and 1299.8 ± 1833.4 mg/day in the 200-mg cohort, versus 88.7 ± 259.29 mg/day in the placebo group. ISIS 388626 induced a reversible increase in serum creatinine, with the largest effect after eight doses of ISIS 388626 (200 mg; 0.38 ± 0.089 mg/dl; 44% increase over baseline). Three subjects were discontinued as a result of creatinine increases. The renal clearance test revealed no indications for impairment of glomerular filtration or renal perfusion. The creatinine increases were accompanied by a rise in the levels of urinary renal damage markers [β-2-microglobulin (B2M), total protein, kidney injury molecule (KIM1), α-glutathione S-transferase (aGST), N-acetyl-β-(d)-glucosaminidase (NAG)]. Other treatment-related adverse events included mild injection site reactions occurring in 8-19% of the subjects. In conclusion, ISIS 388626 treatment induced glucosuria at a dose level of 200 mg/week. This intended pharmacological effect was small, amounting to approximately 1% of the total amount of filtered glucose. Changes in serum and urinary markers were indicative of transient renal dysfunction, most probably of tubular origin. Whether the glucosuria is caused by specific SGLT2 inhibition or general tubular dysfunction or a combination remains uncertain.

4020 Background: Patients (pts) with anal squamous cell carcinoma (ASCC) have poor outcomes and few treatment options. We report a pooled analysis of pembrolizumab (pembro) antitumor activity and safety in the ASCC cohorts of the multicohort studies KEYNOTE-028 (NCT02054806; phase 1b) and KEYNOTE-158 (NCT02628067; phase 2), providing a robust sample size and longer follow-up. Methods: Eligible pts were aged ≥18 y with histologically/cytologically confirmed metastatic/unresectable ASCC, had prior failure of/intolerance to standard therapy or no standard therapy options, measurable disease (RECIST v1.1), ECOG PS 0/1, and a tissue sample evaluable for PD-L1/biomarkers (KEYNOTE-028 required PD-L1 positivity). Baseline PD-L1 expression was assessed using a prototype IHC assay (QualTek) in KEYNOTE-028 and the PD-L1 IHC 22C3 pharmDx assay (Agilent Technologies) in KEYNOTE-158. Pts received pembro 10 mg/kg Q2W (KEYNOTE-028) or 200 mg Q3W (KEYNOTE-158) for 2 y or until PD/unacceptable AEs. The primary endpoint in both studies was ORR (per RECIST v1.1). Secondary endpoints were duration of response (DOR), PFS, OS, and safety. Results: 137 pts with ASCC were treated in KEYNOTE-028 (n = 25) or KEYNOTE-158 (n = 112) and were included in this analysis (median age, 61 y; 83.2% women; 73.0% had PD-L1–positive tumors). Median follow-up was 11.7 mo; 124 pts (90.5%) had discontinued treatment. ORR (95% CI) was 10.9% (6.3%–17.4%). 8 pts had CR and 7 had PR. ORR (95% CI) by PD-L1 status was 14.0% (7.9%–22.4%) in the PD-L1 positive group and 3.3% (0.1%–17.2%) in the PD-L1 negative group. Among all treated pts, median DOR was not reached (range, 6.0+ to 57.5+ mo). By Kaplan-Meier estimation, 84.6% of responders had a DOR ≥24 mo. Median PFS was 2.1 mo (95% CI, 2.0–2.1) and median OS was 11.7 mo (95% CI, 8.8–14.5). The 12-mo PFS and OS rates were 14.5% and 47.4%. 85 pts (62.0%) had +1 treatment-related AE, 24 pts (17.5%) with grade 3–4 events (no grade 5 events). 32 pts (23.4%) had immune-mediated AEs; 2 pts (1.5%) had infusion related reactions. Conclusions: In pts with previously treated advanced ASCC, pembro showed durable antitumor activity, particularly in pts with PD-L1–positive tumors, and manageable toxicity. Clinical trial information: NCT02054806 (KEYNOTE-028), NCT02628067 (KEYNOTE-158) .

The antisense compound ISIS 388626 selectively inhibits renal glucose reabsorption by inhibiting the sodium–glucose cotransporter‐2 (SGLT2) mRNA expression. It is developed as an insulin‐independent treatment approach for type 2 diabetes mellitus (T2DM). The safety, tolerability, pharmacokinetics, and pharmacodynamics after subcutaneous administration of the drug were planned to be evaluated in healthy volunteers in a single‐ascending‐dose study (50–400 mg) and a multiple‐ascending‐dose study (6 weeks; weekly doses of 50–400 mg with loading dose regimen of three doses during the first week). The study was halted early because increases in serum creatinine occurred in the subjects participating in the 100 mg multiple‐dose cohort. The pronounced changes in serum creatinine were accompanied by increased urinary excretion of beta‐2‐microglobulin and KIM1. The possible mechanisms for these findings remain elusive and are in contrast to preclinical findings as comparable treatment with ISIS 388626 of animals did not reveal similar changes. Although exposure was limited, there was an indication that glucosuria increased upon active treatment. Before the concept of antisense‐mediated blocking of SGLT2 with ISIS 388626 can be explored further, more preclinical data are needed to justify further investigations.