"Bottom Line The investigational anticancer therapeutic abemaciclib which targets CDK and CDK showed durable clinical activity when given as continuous singleagent therapy to patients with a variety of cancer types including breast cancer nonsmall cell lung cancer NSCLC glioblastoma and melanoma according to results from a phase I clinical trial. Journal in Which the Study was Published Cancer Discovery a journal of the American Association for Cancer Research. Senior authors Amita Patnaik MD associate director of clinical research at South Texas Accelerated Research Therapeutics in San Antonio Texas and Geoffrey I. Shapiro MD PhD director of the Early Drug Development Center at the DanaFarber Cancer Institute in Boston. Background In February  the U.S. Food and Drug Administration FDA approved the CDK inhibitor palbociclib Ibrance for use in combination with the aromatase inhibitor letrozole for treating postmenopausal women with estrogen receptorpositive HERnegative advanced breast cancer. The oral CDK inhibitor abemaciclib is a very different molecule from palbociclib with distinct attributes that contribute to its discrete therapeutic effects in particular its singleagent activity according to Shapiro. For example abemaciclib has greater selectivity for CDK compared with palbociclib which may explain why it does not affect white blood cell counts as severely allowing it to be taken on a continuous schedule without treatment holidays he said. Abemaciclib also penetrates the central nervous system whereas palbociclib does not raising the possibility that it could be used to treat primary or metastatic brain tumors he added. How the Study Was Conducted and Results Patnaik Shapiro and colleagues enrolled  patients with a variety of types of advanced cancer in the phase I clinical trial designed to evaluate the safety and preliminary efficacy of abemaciclib. In the dose escalation phase the researchers determined that the maximum tolerated dose was  milligrams mg every  hours the doselimiting toxicity was grade  fatigue. In the expansion phase singleagent abemaciclib was administered to  patients with breast cancer  with NSCLC  with glioblastoma  with melanoma and  with colorectal cancer. Among these patients the most common treatmentrelated adverse events were fatigue diarrhea nausea vomiting anorexia weight loss kidney dysfunction and decreased red and white blood cell counts. Radiographic responses were observed for some patients with breast cancer NSCLC and melanoma. Among the  patients with hormone receptorpositive breast cancer  had a partial response with four of the  responders having continued prior endocrine therapy and an additional  patients had stable disease. Among the  patients with NSCLC two had a partial response and  had stable disease one patient who had a partial response and  who had stable disease were known to have KRASmutant NSCLC. Among the  patients with melanoma one had a partial response and six had stable disease. Three of the  patients with glioblastoma had stable disease with two of them continuing to receive treatment without disease progression for  and  cycles respectively. Author Comment These data show that abemaciclib is an oral drug that can be taken on a continuous schedule and achieve durable clinical activity against multiple tumors including breast and lung cancers said Shapiro. The results of the trial supported the FDA decision to grant breakthrough therapy designation to abemaciclib previously known as LY for patients with refractory hormone receptorpositive advanced or metastatic breast cancer added Patnaik. Limitations Patnaik explained that because this study included  patients with different types of cancer confirmatory clinical trials in specific patient populations are necessary to precisely define the role of abemaciclib in cancer care. Multiple clinical trials have already been initiated to evaluate abemaciclib as a treatment for certain groups of patients with breast cancer and NSCLC as well as children with primary brain tumors and adults with brain metastases she noted.  Funding  Disclosures The study was funded by Eli Lilly and Company. Patnaik has received research funding from Lilly. Shapiro served on an advisory board for Lilly during the conduct of the study reports receiving personal fees from Lilly GI Therapeutics Vertex Pharmaceuticals and grants from Lilly for work other than reported here and is an investigator on several trials using other CDK inhibitors including palbociclib and ribociclib. Follow us Cancer Research Catalyst httpblog.aacr.org Twitter AACR and Facebook http About the American Association for Cancer Research Founded in  the American Association for Cancer Research AACR is the worlds first and largest professional organization dedicated to advancing cancer research and its mission to prevent and cure cancer. AACR membership includes more than  laboratory translational and clinical researchers population scientists other health care professionals and patient advocates residing in  countries. The AACR marshals the full spectrum of expertise of the cancer community to accelerate progress in the prevention biology diagnosis and treatment of cancer by annually convening more than  conferences and educational workshops the largest of which is the AACR Annual Meeting with nearly  attendees. In addition the AACR publishes eight prestigious peerreviewed scientific journals and a magazine for cancer survivors patients and their caregivers. The AACR funds meritorious research directly as well as in cooperation with numerous cancer organizations. As the Scientific Partner of Stand Up To Cancer the AACR provides expert peer review grants administration and scientific oversight of team science and individual investigator grants in cancer research that have the potential for nearterm patient benefit. The AACR actively communicates with legislators and other policymakers about the value of cancer research and related biomedical science in saving lives from cancer. For more information about the AACR visit http To interview Amita Patnaik or Geoffrey I. Shapiro contact Julia Gunther at julia.guntheraacr.org mailtojulia.guntheraacr.org or ."