Feedback Regulation Of Signaling Research Articles

Cleavage-Mediated Regulation of Myd88 Signaling by Inflammasome-Activated Caspase-1.

Coordination among multiple signaling pathways ensures an appropriate immune response, where a signaling pathway may impair or augment another signaling pathway. Here, we report a negative feedback regulation of signaling through the key innate immune mediator MyD88 by inflammasome-activated caspase-1. NLRP3 inflammasome activation impaired agonist- or infection-induced TLR signaling and cytokine production through the proteolytic cleavage of MyD88 by caspase-1. Site-specific mutagenesis was used to identify caspase-1 cleavage site within MyD88 intermediary segment. Different cleavage site location within MyD88 defined the functional consequences of MyD88 cleavage between mouse and human cells. LPS/monosodium urate–induced mouse inflammation model corroborated the physiological role of this mechanism of regulation, that could be reversed by chemical inhibition of NLRP3. While Toll/interleukin-1 receptor (TIR) domain released by MyD88 cleavage additionally contributed to the inhibition of signaling, Waldenström’s macroglobulinemia associated MyD88L265P mutation is able to evade the caspase-1-mediated inhibition of MyD88 signaling through the ability of its TIRL265P domain to recruit full length MyD88 and facilitate signaling. The characterization of this mechanism reveals an additional layer of innate immunity regulation.

Abstract P5-19-20: A phase I study of MK-2206 in combination with lapatinib in patients with advanced solid tumors followed by dose-expansion in advanced HER2+ breast cancer

Abstract Background : AKT mediates signaling in the human epidermal growth factor receptor-2 (HER2) pathway. HER2 inhibition can result in feedback regulation of signaling, leading to high AKT activity. Preclinical studies demonstrate activity of combined HER2 and AKT inhibition. MK-2206 is an oral selective inhibitor of AKT. This study was designed to determine the maximum tolerated dose (MTD), dose limiting toxicities (DLTs), adverse events (AEs), clinical activity, pharmacokinetic (PK) parameters and explore potential biomarkers of the combination of MK-2206 with lapatinib. Methods : The dose escalation cohort included adult patients (pts) with solid tumors treated with MK-2206 (30-60 mg qod) and lapatinib (1000-1500 mg qd) continuously. Cycles were 28 days, except cycle 1 (35 days), due to a 1 week MK-2206 lead-in to evaluate for PK interactions. MK-2206 plasma concentrations were evaluated on day 1, 9 (steady state) and 15 (steady state in combination with lapatinib). Lapatinib plasma concentrations were evaluated on day 9 (first dose) and day 15 (steady state in combination with MK-2206). Both used a validated LC-MSMS assay. Pharmacokinetic parameters were calculated using non-compartmental methods with WinNonLin Phoenix version. The dose expansion cohort included women with advanced HER2+ breast cancer treated at the MTD. Peripheral blood mononuclear cells (PBMCs) and archived tumor samples were collected for all pts. Results : In the dose escalation cohort, 23 pts (median age 59 [range 22-72];15 female:8 male) were enrolled. Cancers were colorectal (8 pts), lung (4 pts), breast (3 pts) and other (8 pts). 19 evaluable pts were treated a median of 8 weeks (range 3-35). At dose level four, 1 pt had grade 4 hyponatremia, grade 3 rash and hypocalcemia and 1 pt had intolerable grade 2 mucositis with delivery of <75% of drug. The MTD was 45mg po qod of MK-2206 with 1500 mg po qd of lapatinib. The most common AEs at least possibly related to therapy included diarrhea (grade 3-4 in 3 pts; grade 1-2 in 16 pts), nausea (grade 3 in 2 pts; grade 1-2 in 14 pts) and rash (grade 3 in 2 pts; grade 1-2 in 12 patients). PK analyses demonstrated lapatinib half-life was approximately 18 hours on both day 9 and 15. MK-2206 half-life was 65± 119 hours on day 1, 104± 84 on day 9 and 59.1±25 on day 15. Dose adjusted MK-2206 AUC (hr*ng/mL/mg) was 26.6± 31 of day 1, 100.6± 78 on day 9 and 62.8± 58 on day 15. In the dose expansion cohort, five HER2+ women were enrolled (median age 43 yrs [range 33-56]). The majority were heavily pretreated: all had prior progression on trastuzumab and 2 with prior lapatinib. They were on study for a median of 8 weeks (range 4-24 weeks). One pt had stable disease for 6 months and another pt had clinical benefit with non-measurable skin disease and she remains on study. Exploration of PBMCs for evidence of target inhibition in HER2-PI3K-AKT signaling and tumor tissue for PTEN loss, PI3K mutations will be presented. Conclusions : Continuous dosing of MK-2206 in combination with lapatinib is well-tolerated. Preliminary results of pharmacokinetic analysis indicate a potential for a drug interaction. Clinical benefit was seen in patients with HER2+ breast cancer. Citation Format: Moniba Nazeef, Amye J Tevaarwerk, Jens Eickhoff, Mark E Burkard, Jennifer Heideman, Glenn Liu, Chris Flynn, Jill M Kolesar, Kari B Wisinski. A phase I study of MK-2206 in combination with lapatinib in patients with advanced solid tumors followed by dose-expansion in advanced HER2+ breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-19-20.

A phase I study of MK-2206 in combination with lapatinib in patients (pts) with advanced solid tumors.

2607 Background: The AKT protein kinase is a key mediator of signaling in the human epidermal growth factor receptor-2 (HER2) pathway. HER2 inhibition can result in feedback regulation of signaling, leading to high AKT activity. Preclinical studies demonstrate activity of combined HER2 and AKT inhibition. Lapatinib is an oral tyrosine kinase inhibitor of HER2. MK-2206 is an oral selective inhibitor of AKT with a maximum tolerated dose (MTD) of 60mg qod. Both agents cause rash and diarrhea. This study was designed to determine the MTD, dose limiting toxicities (DLTs), adverse events (AEs), clinical activity and pharmacokinetic (PK) parameters of the combination. Methods: This phase I study evaluated the safety of MK-2206 (30-60 mg qod) and lapatinib (1000-1500 mg qd) continuously. Cycles were 28 days, except cycle 1 (35 days), due to a 1 week MK-2206 lead-in to evaluate for PK interactions. Because of the continuous nature of therapy, protocol-specified intolerable grade 2 AEs were considered DLTs during cycle 1. Results: 23 pts (median age 59 [range 22-72];15 female:8 male) were enrolled. The most common malignancies were colorectal (8 pts), lung (4 pts), and breast (3 pts). 4 pts were unevaluable per protocol; 19 evaluable pts were on study a median of 8 weeks (range 3-35). 3 pts experienced DLTs. At dose level one, 1 pt had grade (gr) 3 hyponatremia and fatigue. At dose level four, 1 pt had gr 4 hyponatremia, gr 3 rash and hypocalcemia and 1 pt had intolerable gr 2 mucositis with delivery of <75% of drug. The most common AEs at least possibly related to therapy included diarrhea (gr 3-4 in 3 pts; gr 1-2 in 16 pts), nausea (gr 3 in 2 pts; gr 1-2 in 14 pts) and rash (gr 3 in 2 pts; gr 1-2 in 12 pts). The MTD was 45mg po qod of MK-2206 with 1500 mg po qd of lapatinib, exceeding biologically active doses for each agent. One pt with adrenal cortical carcinoma was on study for 6 months with stable disease (SD) and 1 pt with colorectal cancer was on study for 5 months with significant tumor marker decline and SD. PK analyses are ongoing. Conclusions: MK-2206 in combination with lapatinib is well-tolerated at biologically active single agent doses. Anti-tumor activity will be evaluated further in a dose expansion cohort in pts with advanced HER2-positive breast cancer. Clinical trial information: NCT01245205.