SAM Competitive PRMT5 Inhibitor PF-06939999 Demonstrates Antitumor Activity in Splicing Dysregulated NSCLC with Decreased Liability of Drug Resistance

Protein arginine methyltransferase 5 (PRMT5) over-expression in hematological and solid tumors methylates arginine residues on cellular proteins involved in important cancer functions including cell cycle regulation, mRNA splicing, cell differentiation, cell signaling, and apoptosis. PRMT5 methyltransferase function has been linked with high rates of tumor cell proliferation and decreased overall survival, and PRMT5 inhibitors are currently being explored as an approach for targeting cancer-specific dependencies due to PRMT5 catalytic function. Here we describe the discovery of potent and selective S-adenosylmethionine (SAM) competitive PRMT5 inhibitors, with in vitro and in vivo characterization of clinical candidate PF-06939999. Acquired resistance mechanisms were explored through the development of drug resistant cell lines. Our data highlight compound-specific resistance mutations in the PRMT5 enzyme that demonstrate structural constraints in the co-factor binding site that prevent emergence of complete resistance to SAM site inhibitors. PRMT5 inhibition by PF-06939999 treatment reduced proliferation of NSCLC cancer cells, with dose-dependent decreases in symmetric dimethyl arginine (SDMA) levels and changes in alternative splicing of numerous pre-mRNAs. Drug sensitivity to PF-06939999 in NSCLC cells associates with cancer pathways including MYC, cell cycle and spliceosome, and with mutations in splicing factors such as RBM10. Translation of efficacy in mouse tumor xenograft models with splicing mutations provides rationale for therapeutic use of PF-06939999 in the treatment of splicing dysregulated NSCLC.

Voluntary certification and the uniform guidelines on selection procedures: a potential problem for personnel managers

Employers in health care sometimes rely upon various standardized testing procedures in selecting, promoting, and training personnel. Within the health professions, voluntary certification programs have developed to permit individuals to demonstrate competence and become recognized as qualified practitioners. This article addresses the problems which can occur, but are not widely recognized, when employers use voluntary certification examinations in the selection process. The impact of the federal government's "Uniform Guidelines on Employee Selection Procedures" upon voluntary certification activities is uncertain at best, and frightening, at worst. While the Guidelines require employers to use only validated examinations where adverse impact upon protected minority groups exists, they do not effectively address the use of professional certifying examinations and fail to provide guidance for either certifying agencies or employers. This leaves great potential for conflict, since circumstances in which employment is terminated, an employee denied promotion, or even denied opportunities for entry into positions based on an employer's use of voluntary certifying examinations, are increasing daily. How does an employer validate a national certifying examination that he does not administer? How does the certifying agency protect itself from allegations of discrimination or anti-trust violations based on actions of an employer with whom the agency has no contact? This article offers no answers to these troublesome questions. However, it may help eliminate another problem noted by the author--widespread ignorance of the seriousness of these circumstances for employers and certifying agencies. From first-hand experience and research into the development of the Uniform Guidelines, the author points out many of the difficulties which await those who rely on non-validated examinations or choose to ignore the government's edict that examinations used in selection must have a demonstrated relationship to the job. Finally, the article proposes solutions to the dilemma faced by certifying organizations and suggests that, by becoming more aware of the Uniform Guidelines, employers and testing groups have the opportunity to protect themselves before a problem occurs.