The primary objective was to evaluate intracranial objective response rate (iORR) in patients receiving abemaciclib with brain or leptomeningeal metastases (LM) secondary to hormone receptor-positive (HR þ) metastatic breast cancer (MBC). Secondary objectives evaluated extracranial response, abemaciclib pharmacokinetics, brain metastases tissue exposure, and safety. Patients and Methods: This nonrandomized, phase II study (NCT02308020) enrolled patients in tumor subtype-specific cohorts AD: A (HR þ , HER2 À MBC), B (HR þ , HER2 þ MBC), C (HR þ MBC LM), and D (brain metastases surgical resection). Abemaciclib 200 mg was administered twice daily as monotherapy or with endocrine therapy, or 150 mg twice daily with trastuzumab. Cohorts A and B used a Simon two-stage design. Results: In cohort A (n ¼ 58), 3 patients were confirmed responders resulting in an iORR of 5.2% [95% confidence interval (CI), 0.0-10.9], and the intracranial clinical benefit rate (iCBR) was 24% (95% CI, 13.1-35.2). Median overall survival (OS) was 12.5 months (95% CI, 9.3-16.4). A volumetric decrease in target intracranial lesions was experienced by 38% of patients. In cohort B (n ¼ 27), there were no confirmed intracranial responses. An iCBR of 11% (95% CI, 0.0-23.0) was observed. Median OS was 10.1 months (95% CI, 4.2-14.3). A volumetric decrease in target intracranial lesions was experienced by 22% of patients. In cohort C (n ¼ 10), one confirmed complete parenchymal response was observed. In cohort D (n ¼ 9), unbound brain metastases concentrations of total active abemaciclib analytes were 96-[cyclindependent kinase 4 (CDK4)] and 19-fold (CDK6) above in vitro IC 50. Safety was consistent with prior studies. Conclusions: This study did not meet its primary endpoint. Abemaciclib was associated with an iCBR of 24% in patients with heavily pretreated HR þ , HER2 À MBC. Abemaciclib achieved therapeutic concentrations in brain metastases tissue, far exceeding those necessary for CDK4 and CDK6 inhibition. Further studies are warranted, including assessing novel abemaciclibbased combinations.
Background
IMI2-PainCare-BioPain-RCT3 is one of four similarly designed clinical studies aiming at profiling a set of functional biomarkers of drug effects on the nociceptive system that could serve to accelerate the future development of analgesics, by providing a quantitative understanding between drug exposure and effects of the drug on nociceptive signal processing in human volunteers. IMI2-PainCare-BioPain-RCT3 will focus on biomarkers derived from non-invasive electroencephalographic (EEG) measures of brain activity.
Methods
This is a multisite single-dose, double-blind, randomized, placebo-controlled, 4-period, 4-way crossover, pharmacodynamic (PD) and pharmacokinetic (PK) study in healthy subjects. Biomarkers derived from scalp EEG measurements (laser-evoked brain potentials [LEPs], pinprick-evoked brain potentials [PEPs], resting EEG) will be obtained before and three times after administration of three medications known to act on the nociceptive system (lacosamide, pregabalin, tapentadol) and placebo, given as a single oral dose in separate study periods. Medication effects will be assessed concurrently in a non-sensitized normal condition and a clinically relevant hyperalgesic condition (high-frequency electrical stimulation of the skin). Patient-reported outcomes will also be collected. A sequentially rejective multiple testing approach will be used with overall alpha error of the primary analysis split between LEP and PEP under tapentadol. Remaining treatment arm effects on LEP or PEP or effects on EEG are key secondary confirmatory analyses. Complex statistical analyses and PK-PD modeling are exploratory.
Discussion
LEPs and PEPs are brain responses related to the selective activation of thermonociceptors and mechanonociceptors. Their amplitudes are dependent on the responsiveness of these nociceptors and the state of the pathways relaying nociceptive input at the level of the spinal cord and brain. The magnitude of resting EEG oscillations is sensitive to changes in brain network function, and some modulations of oscillation magnitude can relate to perceived pain intensity, variations in vigilance, and attentional states. These oscillations can also be affected by analgesic drugs acting on the central nervous system. For these reasons, IMI2-PainCare-BioPain-RCT3 hypothesizes that EEG-derived measures can serve as biomarkers of target engagement of analgesic drugs for future Phase 1 clinical trials. Phase 2 and 3 clinical trials could also benefit from these tools for patient stratification.
Trial registration
This trial was registered 25/06/2019 in EudraCT (2019%2D%2D001204-37).
Although Aurora A, B, and C kinases share high sequence similarity, especially within the kinase domain, they function distinctly in cell-cycle progression. Aurora A depletion primarily leads to mitotic spindle formation defects and consequently prometaphase arrest, whereas Aurora B/C inactivation primarily induces polyploidy from cytokinesis failure. Aurora B/ C inactivation phenotypes are also epistatic to those of Aurora A, such that the concomitant inactivation of Aurora A and B, or all Aurora isoforms by nonisoform-selective Aurora inhibitors, demonstrates the Aurora B/C-dominant cytokinesis failure and polyploidy phenotypes. Several Aurora inhibitors are in clinical trials for T/B-cell lymphoma, multiple myeloma, leukemia, lung, and breast cancers. Here, we describe an Aurora A-selective inhibitor, LY3295668, which potently inhibits Aurora autophosphorylation and its kinase activity in vitro and in vivo, persistently arrests cancer cells in mitosis, and induces more profound apoptosis than Aurora B or Aurora A/B dual inhibitors without Aurora B inhibition-associated cytokinesis failure and aneuploidy. LY3295668 inhibits the growth of a broad panel of cancer cell lines, including smallcell lung and breast cancer cells. It demonstrates significant efficacy in small-cell lung cancer xenograft and patient-derived tumor preclinical models as a single agent and in combination with standard-of-care agents. LY3295668, as a highly Aurora A-selective inhibitor, may represent a preferred approach to the current pan-Aurora inhibitors as a cancer therapeutic agent.
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