NCI Initiatives to Develop Non-Clinical Models for Pediatric Oncology Malcolm A. Smith, MD, PhD 17 March 2004

Drug Development Pyramid Many more agents are evaluated in phase I trials for adults than can be systematically evaluated in phase I trials in children Even fewer new agents can be evaluated in phase II trials in children For most solid tumors of children, only 1 phase III study can be conducted every 4-5 years The challenge: How to pick the right agents?? Phase III Phase I Studies in Children Phase II Phase I Studies in Adults

Neuroblastoma Example – Drugs under evaluation with potential applicability to neuroblastoma Decitabine Fenretinide Interleukin-12 Trk tyrosine kinase inhibitor Oxaliplatin HDAC inhibitors (e.g., depsipeptide) BSO Potential for multiple combinations of the above with standard chemotherapy and with other novel agents Which for phase 3 evaluation???

The need for non-clinical testing? Predictive non-clinical methods may contribute to prioritizing agents for evaluation against specific types of childhood cancer A systematic approach to non-clinical testing is required to assess the predictive value of pediatric non-clinical models NCI Board of Scientific Advisors approved committing $10 million to this effort over the next 5 years through Pediatric Preclinical Testing Program

Role of xenografts in drug development – Adult experience Overall activity across range of tumor xenografts predicts for eventual clinical success in at least one tumor type Johnson, et al. Br J Cancer 2001; 84(10): Using panels of xenografts for a given tumor type increases the likelihood for correct prediction. Voskoglou-Nomikos, et al. Clin Cancer Res 2003; 9(11): Human Tumor Xenografts as Predictive Preclinical Models for Anticancer Drug Activity in Humans: Better than Commonly Perceived —But They Can Be Improved Kerbel, Cancer Biol Ther Jul-Aug;2(4 Suppl 1):S134-9

Panels of Xenograft Lines Enhance Predictive Value Voskoglou-Nomikos, et al. Clin Cancer Res 2003; 9(11):

Contribution of Pharmacology to Enhancing Predictive Ability of Preclinical Models Predictive ability of xenografts can likely be enhanced by comparisons of mouse pharmacology to human pharmacology. Pharmacology can rule out the trivial explanation for activity in xenograft models: Mice tolerate much more of the agent than humans, and human cancers implanted in mice are exposed to much higher levels than would ever occur in the clinical setting.

Why Pediatric Preclinical Models May Be More Useful than Adult Models Pediatric drug development decision-making can utilize both: Pediatric non-clinical testing results Comparison of mouse PK of agent with PK of agent in initial adult clinical trials Most promising agents are those with activity in pediatric models at serum levels achievable in humans Example incorporating PK of positive prediction from pediatric literature : irinotecan Example incorporating PK of correctly predicting inactivity: sulofenur

Pediatric Preclinical Testing- The Potential for Prediction The activity of agents in rhabdomyosarcoma xenografts mirrors the clinical activity of these agents Topoisomerase I inhibitors prospectively identified in xenograft models as active agents against rhabdomyosarcoma and neuroblastoma Preclinical in vivo models available for many childhood cancers

Patient and NOD/SCID peripheral blood smears Patient #10 c-ALL Patient #11 c-ALL Patient NOD/SCID Lock, et al. Blood. 2002;99: 4100, 2002

In vivo responses of childhood ALL to vincristine in NOD/SCID mice Weeks Post Treatment B. Saline Weeks Post Treatment % Human CD45 + Cells in Peripheral Blood A. Vincristine Lock, et al. Blood. 2002;99: 4100, 2002

In vivo sensitivity to vincristine correlates with length of CR1 Lock, et al. Blood. 2002;99: 4100, 2002

Molecularly Targeted Agents: Preclinical PK/PD comparisons Especially important in era of molecular targets. Can identify degree of target modulation that is associated with antitumor activity. Can identify the duration of target modulation that is associated with antitumor activity. Identify serum levels (systemic exposure) of agent associated with requisite levels of target modulation. Opportunity to correlate antitumor activity with gene expression profiles and with protein expression profiles.

Pediatric Oncology Preclinical Protein and Tissue Array Project (POPP-TAP) Collaboration between NCI & COG researchers To develop tissue and cell arrays and protein lysate arrays of pediatric preclinical cancer models To determine gene expression profiles for pediatric preclinical cancer models To facilitate conduct & interpretation of preclinical testing of “targeted” agents in childhood cancer models

Complicating factors in testing molecularly targeted agents: Promiscuity of agent: a targeted agent hits multiple targets (some recognized, some not) Bay (Raf kinase inhibitor) Multiple biological effects of modulating target (one target affects multiple downstream pathways) Farnesyltransferase inhibitors (e.g., R115777) Proteasome inhibitors (e.g., PS-341) Hsp90 inhibitors (e.g., 17-AAG) Potential applicability of agents with broadly expressed targets is difficult to assess prospectively Preclinical testing may allow identification of previously unrecognized activities or interactions and may allow identification of unanticipated activity

What are the alternatives? Mouse genetic models have made important contributions to our understanding of cancer pathogenesis. Genetically engineered models must have specific properties in order to be suitable for drug testing: short latency and high penetration. Some genetically engineered models for pediatric cancers that are suitable for drug testing (e.g., MYCN) A mouse is a mouse, and mouse biology is not the same as human biology (Rangarajan and Weinberg, Nature Cancer Reviews 3:952, 2003) Models based upon more “humanized” mice may more faithfully replicate human cancers.

NCI Pediatric Preclinical Testing Program Based on panels of xenograft lines for most common childhood cancers Incorporates in vitro testing component Systematic testing of agents per year Seek to obtain agents near time that commitment to initial clinical evaluation in adults is made Implemented via contract mechanism with primary contractor and with potential for subcontracts for testing specific cancer types

Clin Cancer Res 2002; 8(12):

Addressing Intellectual Property Issues NCI efforts over past 2 years to develop a Model MTA that will be used (with only minor modifications) for all transfers by companies of their proprietary compounds to NCI- supported investigators for preclinical testing Acceptance of Model MTA is requirement for participation in Pediatric Preclinical Testing Program Dr. Sherry Ansher is CTEP contact for inquiries about Model MTA

Summary Appropriate prioritization is key to future treatment advances for childhood cancer NCI’s Pediatric Preclinical Testing Program may contribute to successful prioritization Systematic preclinical testing of all agents entering clinical evaluation in children should become the “standard of care” Systematic preclinical testing will allow validation and optimization of pediatric preclinical tumor panels