New Directions for Sickle Cell Therapy in the Genome Era

New Directions for Sickle Cell Therapy in the Genome Era

Working Group Reports

Thursday, November 20, 2003

For the second day of the conference, each attendee participated in two working groups. Each working group discussed one of five topics: the therapeutic implications of phenotypic diversity; hemoglobin switching; gene transfer; small molecule/chemical genomics approaches to SCD; and the historical, cultural, and social context of clinical research in SCD. Reports from these working groups are presented under the Friday session, immediately below.

Friday, November 21, 2003

On Friday, each of the five working group reports mentioned directly above were presented to the entire group of attendees, who then discussed them. The reports and points from the subsequent discussions follow:

Report from the Therapeutic Implications of Phenotypic Diversity Working Groups

  1. Where are we now?
    • Enormous phenotypic diversity in sickle cell disease
    • Inability to predict acute and chronic complications makes management of sickle cell disease very challenging
    • Multitude of current and emerging therapies that aim to interrupt sickling process itself and vaso-occlusion at several key pathways
    • Not all agents are effective in all patients
    • Agents and procedures are not without risk
       
  2. What do we mean by phenotypic diversity?
    • The parameters for stratification of sickle cell disease patients into severity or organ specific groups need to be defined by a working group, evolving into a consensus statement of specific robust phenotypic criteria.
    • The creation of these criteria will serve as a basis for consistency in clinical trials as well as for large-scale genotype-phenotype association studies.
    • Incorporating this into a database of patients eligible for clinical research should be the eventual outcome
       
  3. What is the ultimate goal for the field?
    • Need risk stratification to facilitate assignment of appropriate treatment
    • To be able to stratify risk, the genetic basis of the phenotypic variability needs to be understood
    • Design intervention studies to prevent or minimize complications of sickle cell disease
       
  4. What is the science needed?
    • Innovative techniques to improve phenotypic definition at all levels:
      • Clinical
      • Laboratory
      • Imaging
      • Newer diagnostic technologies
         
    • Examples of needs:
      • Acute chest syndrome:
        • Defining acute chest syndrome more accurately
        • Improved tests of pulmonary function
        • Use of Micron-CT to evaluate lungs
        • Transcranial Doppler type test for lungs?
      • Stroke:
        • Define more accurately
        • Laboratory tests
        • Evaluation of vascular biology
        • Thrombosis
        • Acute phase reactants
      • Autopsy Data
         
  5. What critical elements can help achieve these goals in the short term?
    • Recruit a group to establish criteria for defining phenotypic diversity and create a clinical consortium to share this resource. In tandem regional referral labs for genotyping, novel research tests, and DNA/plasma repositories with patients enrolled with human subjects guidelines in place at the outset.
    • A centralized web-based registry with open access
    • In order to accomplish the above two elements an educational program for patients, families, communities, and primary care providers is critical
    • Establishment of international collaborations is essential to help define the environmental/genetic contribution to sickle cell disease via twin/sib-pair studies and studies of unusually mild phenotypes in long-term survivors
       
  6. What role should the NIH play in helping the community achieve these goals?
    • Sickle cell disease should be the prototype disease to apply the consequences of the Human Genome Project and its evolving technologies to accelerate new knowledge and treatment.
    • The NIH may accomplish this through its funding resources, leadership, and incorporation of the International community.
    • The NIH should require maximal sharing of data and resources that are developed with public funding.

Discussion following the therapeutic implications of phenotypic diversity working groups' report included these other points:

  • The Cooperative Study of Sickle Cell Disease (CSSCD) database available on CD-ROM; the Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH) clinical data is owned by investigators, but will work to get access; barriers to access are a significant current problem.
  • Need prospective databases of all patients being followed that includes genotypes; many current studies do not include DNA
  • Need long-term thinking about disease - after all, it is a genetic disease that will continue to involve generations to come. Need a smaller, well-defined group to work on this that includes people that are knowledgeable in current technologies.
  • Current groups working on SCD are not working together sufficiently and are inefficient
  • Get working groups together to develop standards that investigators can use as guidelines when developing studies
  • A huge investment is needed to cast a wide enough net to gather the data needed - NIH alone cannot fund this, we need to get advocacy community involved
  • Who are the best people to do this kind of work? Clinicians, experts in genomics, experts in high-throughput are not the same people. We need to share knowledge and work together but also to develop a new group of researchers that are comfortable and knowledgeable in all areas.
  • Explore the SCD patients who are living longer than expected
  • Shouldn't neglect studying phenotypic diversity in mouse models, as it could provide clues that might parallel humans.

Report from the Hemoglobin Switching Working Groups

Note: All recommendations in this report are predicated on the infusion of new disciplines, new investigators and increased manpower into the field. There is need for multidisciplinary (biophysics, imaging, informatics, physical chemistry, etc.) teams and for innovative programs to attract and retain these new investigators.

  1. Support for development of a new model to study hemoglobin F reactivation
    • New cell systems are needed, including human adult cell lines (expressing gamma and beta globin) that are responsive to switching agents. Primary cells or cell lines e.g., human embryonic stem cells
       
  2. Resources for drug development for sickle cell disease, to include:
    • Non-human primate testing for comparative activity and pharmacokinetics
    • Resources for preclinical toxicology screens (rodent and non-rodent)
    • Infrastructure for Phase I and II clinical trials
    • Three classes of drugs already screened
       
  3. Genomics tools "service center"
    • High density haplotype map in African Americans and other populations relevant to sickle cell disease
    • Whole genome microarrays
    • Web site/database and central facility to send data for analysis
       
  4. Core resource facilities
    • Transgenic mice generation and dissemination for performing drug screening
    • Depository for critical DNA constructs and cell lines
    • Large-scale source of CD34 cells
    • Antibodies for sorting erythroid progenitor cells and methylated/acetylated DNA
       
  5. Development of new genomic-based technologies for:
    • 3-D imaging of regulatory domains and chromatin structure
    • Exploring structure of DNA super molecule
    • Step-by-step analysis of activation complex formation in each globin gene
    • Identification of all components of regulatory complexes to help target therapies
    • Interference of complexes
       
  6. Novel approaches to the reactivation of hemoglobin F
    • Signal transduction variables explored in a comprehensive fashion, looking at intra-nuclear and extra-nuclear factors
    • Post-transcriptional models
    • Program of hemoglobin F expression in adult vs. fetal erythropoiesis
       
  7. Access to clinical trials database and DNA
    • From the Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH), the Cooperative Study of Sickle Cell Disease (CSSCD), the Stroke Prevention Trial in Sickle Cell Anemia (STOP), etc.
    • Repository of DNA from patients with high and low hemoglobin F levels, pre and post hydroxyurea
    • Support hemoglobin F assays in ongoing unrelated clinical drug trials.

Discussion following the hemoglobin switching working groups' report included these other points:

  • Need to distinguish between developmental hemoglobin switching and reactivation of hemoglobin F in adult cells - both of which are important.
  • Need to pursue knowledge of mechanisms to develop better drugs based on new and more sophisticated high throughput screening assays; but also need to push to move existing candidate drugs through Phase I and II
  • May want combination treatment for patients; however, an obstacle to this is that FDA will not let two unapproved drugs be in a trial together
  • Need to promote true translational research (current weakness in system)
  • Consequences of the sickle cell mutation for overall gene expression have not been explored systematically - use microarrays and proteomics on various tissues to look at gene and protein expression and how that differs between sickle cell disease and normal tissues, and between equilibrium state and crisis.

Report from the Gene Transfer Working Groups

  1. Safety
    • Short Term: Need to continue to improve current vector technology and assessment of safety issues related to them.
    • Long Term: Need to develop new and better vectors and gene transfer systems, includes non-integrating strategies, targeted integration and homologous recombination.
    • In Parallel With These Studies: Need to develop stem cell purification, expansion and modification while preserving function. Also needed are assays for the number, function and quality control of modified cells.
       
  2. Stem Cell Biology
    • Myeloablation: Need hypothesis-driven research into the relationship between the degree of myeloablation and chimerism
    • In Vivo Selection And Amplification: Need to develop human surrogate assays for human stem cell transduction, and large animal models which can be used to develop pharmacological and biological controlled stem cell amplification
    • Allogeneic Transplantation: Support the participation of people of African descent in SNP and diversity studies and as well as the BMT registry
    • Both gene therapy and allogeneic transplantation would benefit from the development of better immune suppression strategies
       
  3. Biomarkers
    • Need to discover sensitive and reliable biomarkers for disease severity, disease progression and clinical improvement
    • Biomarkers are applicable to both the clinical management of sickle cell disease and future clinical trials
       
  4. Recommendations
    • Strengthen the role of the NIH in the dissemination of biologicals, cytokines, animals and patient materials for sickle cell disease gene therapy
    • Use the resources of the NIH to educate and inform the public and investigators with a realistic review of opportunities in gene therapy research and applications. The goal of this is to influence the career choice of young investigators that will translate into therapies for sickle cell disease through funding opportunities
    • Encourage Cord Blood Banks to collect SS and thalassemia cells. These have potential for future treatment and research
    • Develop human SS ES cells

Discussion following the gene transfer working groups' report included these other points:

  • Application of lentivirus approaches to hemoglobinopathies - animal studies, of course; however, consensus, if any, was that momentum is building; issues of safety is paramount, but also confident that clinical trials will come soon
  • Perhaps set up some guidelines to be used as yardstick for safety. Maybe FDA should set down guidelines as to what this would require
  • Field cannot tolerate a gene transfer trial that harms
  • Development of young investigators is important; there are training possibilities available, but people are not sufficiently aware of them - need help to identify the young investigators and get them in touch with appropriate NIH staff
  • Red cell biology and gene therapy are not "sexy," thus young investigators are not interested-need to let them know that one can make a living doing this
  • Nurse practitioners are an untapped resource; nurses are now trained in genetics-there are nurses that are PI's on projects; need to look into getting nurses involved-this could bridge some of the gaps; enticements might include loan re-payment and mentoring
  • Should NIH specifically support gene therapy trials in thalassemia and SCD; e.g., make clinical grade (GMP) preparations of lentivirus available to investigators, through the National Gene Vector Laboratories?
  • As intermediate measures, sensitive biomarkers are important to safety.

Report from the Small Molecule/Chemical Genomics Working Groups

  1. New Targets: Genomics
    • A large cohort
      • Including patients with sickle cell disease, their family members, and related and unrelated controls
      • Well phenotyped
      • Well consented, prospectively followed, with re-contact possible for follow up
      • Includes genomic DNA and lymphoblastoid cell lines at baseline; serial mRNA, proteome studies through mRNA and plasma at least twice (when asymptomatic and symptomatic)
      • Obligatory sharing of materials (NIMH Genetics Initiative model)
         
    • Proteomics approaches
      • e.g., in depth SS vs. AS vs. AA erythrocytes, "old" vs. "new" SS erythrocytes, etc.
         
    • Transcriptomics
      • Erythroid precursors, reticulocytes, etc.
         
    • Genetic modifier screens
      • Humans
      • Mice
      • Zebrafish
         
  2. Phenotypic Compound Screens
    • Use of NIH Roadmap supported facilities
    • Would detect effects on:
      • Polymerization
      • Phenotypic sickling
    • Would assess compound cell penetrance
    • Use SS cells
      • With attention to heterogeneity to include SS-specific membrane response
    • Use AS cells
      • Minimize cell heterogeneity
         
  3. Target-Based Compound Screens
    • Channels
      • e.g., Gardos channel
    • Iron chelators: better than desferoxamine
    • Hemoglobin F induction: need improved cell lines that make adult hemoglobin (e.g., cord blood or adult erythroid stem cells, embryonic stem cells?)
    • Adhesion assays: need development, better target validation
      • Not yet ready for high throughput screening, but should become so
    • Antithrombotics/anticoagulants?
      • Aspirin, low molecular weight heparin possibilities if magnetic resonance angiography first to rule out small vessel disease
    • Nitric Oxide
      • Can take advantage of work with NO in other areas, e.g., cardiovascular disease
      • Better target validation needed
      • Screen for compounds that will work in physiologic state of SSD
    • Inflammation: less important, needs target validation
    • Oxidation: less important, needs target validation
       
  4. Development of New Animal Models
    • Better utilization of existing animal models
    • Is there a need for better animal models?
      • Nonhuman primates
      • Rabbits
      • Rats
      • Mice
      • Zebrafish
    • Models need to be shared broadly within community
    • Models need to be linked to the human clinical state
       
  5. Preclinical development
    • Need structure for pharmacokinetics, preclinical toxicology, human clinical pharmacology to move sickle cell disease compounds to clinic
    • Existing
      • NCI RAID (Rapid Access to Intervention Development)
    • Translational Research Cores (Roadmap)
       
  6. Clinical trials
    • Need larger and more integrated research network, including but going beyond current Centers
    • DNA collection essential
    • Requires involvement of patient advocacy groups in study design and execution
    • Need governing board to determine study priorities, appropriate endpoints, statistical power - could be done through a formalized clinical research network
    • Studies of psychosocial aspects of disease, incidence, and treatment of co-morbid conditions, e.g., depression
    • Lessons from other disease advocacy groups involvement in clinical trials.

Discussion following the small molecule/chemical genomics approaches to SCD working groups' report included these other points:

  • Bone marrow cells should be made available to the community
  • There is still a lot we don't know about pathophysiology of the disease

Report from the Historical, Cultural, and Social Context of Clinical Research Working Groups

  1. Current Realities
    • Clinical Care
      • Patients and their families have historically faced barriers to clinical care and social services, which has resulted in distrust of the health care system
      • There is a lack of adult medical providers and a resultant lack of continuity of care for adolescents and adults
      • Less than 10% of patients in the United States receive care in comprehensive sickle cell centers, which results in a lack of standardization of care across the United States
         
    • Research
      • There is a dearth of clinical and social researchers
      • There is a dearth of longitudinal studies of sickle cell disease
      • Community based education programs for health professionals, patients and their families are limited
      • There is a lack of researchers studying sickle cell disease
      • There are a limited number of new researchers in the field, as well as a limited number of basic and social science researchers
      • Access to research is limited to 10% of the patient population (NIH SCD Centers and SCD Virtual Centers)
      • International research and international collaborations between researchers and clinical researchers in the USA and abroad are limited
      • More than 95% of patients with sickle cell disease do not live in the United States
         
  2. Where should the field go ultimately?
    Sickle Cell Disease should be the model for the NIH re-engineering of the clinical research enterprise because it lends itself to the fields of: structural, systems and molecular biology; gene therapy; chemical genomics, human variation, clinical investigation, clinical trials; and education, ethical, social, and cultural factors influencing efficacy of medical intervention.

    There should be both a new paradigm and new partnerships for sickle cell disease research. Research on sickle cell disease calls for the establishment of an innovative multidisciplinary sickle cell network and for a new model of research that creates partnerships between communities, clinicians, and researchers.
     
  3. What is the science needed, what are the questions that need to be answered?
    • Data are needed!!!!
    • Longitudinal studies of social, cultural, genetic, and environmental determinants of the disease
    • National and international common data registries that collect genetic, clinical and social environmental information - human genome expertise and collaborative models useful here
       
  4. Recommendations
    1. Establish A Sickle Cell Disease Research Network
      A research network of geographically dispersed centers that would conduct clinical trials and genetic studies is needed.
      • This network would conduct health services research on such issues as standards of care and conduct translational research, such as longitudinal studies of genetic variation of sickle cell disease
      • The network would be a model for clinical, ethical, cultural and social research, as well as for the training of a new cadre of researchers
      • The network would also foster the development of international collaborations
         
    2. Build the Research Workforce Capacity
      There is a need to develop programs to increase the number of clinical researchers, including nurses and allied health professionals, engaged in the research of sickle cell disease.
      • Career development and training mechanisms should be used to increase the number of researchers studying sickle cell disease. This might, for instance, take the form of supplements linked to RO-1, Program Project and Center Grants.
      • Loan repayments programs for clinical researchers, genomic and social science researchers conducting sickle cell disease research should be established, as should loan repayment programs for adult hematologists conducting research and providing clinical care to adult patients
      • The salary cap on K awards should be increased to make them attractive for clinicians to develop a research career in the study of sickle cell disease
         
    3. Develop Model Community Based Participatory Research
      Collaborative partnerships with communities should be developed and communities should be involved in research from its design to its end.
      • RFAs should be developed on:
        • Creating model community and researcher collaborative studies concerning genomic issues
        • International-based research on the ethical, legal, social and cultural implications of conducting genetic research on sickle cell disease
        • Trust and genetic research on sickle cell disease
        • Research of social, cultural barriers to participation in clinical trials and genetic studies
      • Model programs for education for communities, consumers and health professionals should be evaluated
         
    4. Fund Ethical, Legal, Social, and Cultural Research on Sickle Cell Disease
      Ethical, legal, social, and cultural research on sickle cell disease should explore such issues as:
      • How do we understand self-identity, ancestry and race in the context of sickle cell disease?
      • How do we understand stigma and sickle cell disease?
      • Discrimination in employment, insurance, etc.
      • Familial implications for sickle cell disease patients
      • Trustworthiness
      • What are the "best practices" in genetic screening and counseling strategies?
      • International aspects of the ethical, social, and cultural issues of genetic research on sickle cell disease.

Discussion following the historical, cultural, and social context of clinical research in SCD working groups' report included these other points:

  • Need for support of clinical researchers; a critical issue is the requirement for translational clinical researchers involved in trials and treating patients are also trying to run community programs - NIH should fund community coordinators (have lost this type of person over the years) - not just tack an expectation for this activity onto existing grants.
  • Need community studies that emphasize implementation of validated research results into practice in the community
  • Need ways to acknowledge all collaborators in team-oriented research for their work and for such collaboration to figure in academic promotion
  • Need Health Resources and Services Administration (HRSA) and Centers for Disease Control and Prevention (CDC) involvement, too.

General Discussion:

Following these discussions of the working groups' reports was a more general discussion of where SCD research and clinical care should go from here. Prior to this discussion, attendees were asked to cast "votes" among approximately 30 priorities that had emerged during the meeting as options for furthering research aimed at developing new, more effective therapies for SCD. All participants were given 100 votes each, which they could then split among any of the possible priorities. Tabulation of those votes is shown in Appendix C, below.

Among points raised in the discussion were:

  • Other genetic diseases in which research has made inroads may be instructive. For instance, the Cystic Fibrosis Foundation has advanced research by bringing new researchers into the field through feasibility proposals available only to those new to the field, helping plan the path for research, especially regarding a small molecule approach to therapeutics, coordinating various interests in research through an advisory group, developing joint CF Foundation/NIH funding, establishing a CF patient registry, and helping set standards of care for recognized CF clinical centers.
     
  • The experience of the Human Genome Project may also have something to contribute. It provided a model for integration of different types of expertise and for a consortium approach that included shared data resources for which the project demanded no control or ownership, but maintained an expectation for publication and credit that both funders and academia recognized. It also demonstrated that such consortia require leadership, from both inside and outside the NIH, and that they are particularly well suited to attract and integrate new expertise. Other lessons from the Human Genome Project include that to ensure that a shared database can be utilized effectively requires expertise in its development and that curing patients needs to remain the bottom line of biomedical research.
     
  • The paradox that SCD is a monoallelic disease with such variant phenotypes suggests that it involves a complex system and thus a heavy dose of systems biology will be required to understand it. Thus, information from such sources as the Encyclopedia of DNA Elements (ENCODE) will be important to the identification and understanding of remote modifiers and regulators, etc. It would be interesting to focus part of that study on the beta-globin genes.
     
  • The time is right for a whole genome approach to genetic modifiers in SCD.
     
  • Vascular biology is also part of the puzzle, and we will need to use model systems to solve it. Non-invasive means for in vivo studies, such as new imaging techniques, will be important. We need to deal with issues of how to deliver state-of-the-art care and clinical advances from the research arena.

Prof. Sir David Weatherall, Conference Co-Chair, offered observations that included:

  • A key issue is to define the disease at the clinical and phenotypic level to make use of new genomic tools. Thus, we need to move quickly in better defining phenotypes.
  • It may be that the SCD system starts in a stochastic fashion and then modifier genes play a role.
  • We need to think about developing two or three international long-term, sustainable research endeavors.

The other Conference Co-Chair, Francis Collins, noted that:

  • The first part of a revolution is admitting you need one - he heard consensus from the meeting participants that one was needed here and that we need new energy and new disciplines.
  • Centralized databases with open access are important.
  • We need DNA from the parents of those with SCD to look at genetic modifiers.
  • An appropriately powered twin study, by definition international, building on the work of Graham Serjeant is needed.
  • Need large numbers of patients - this requires a shared sense of mission and a shared database.
  • The Haplotype Map (HapMap) will be available soon, which should allow whole genome studies to look for gene modifiers. Nigerian (Yoruba) samples are included. The HapMap will allow taking 300,000-400,000 polymorphisms to do association studies, if pertinent samples are available.
  • NIH-supported chemical genomics centers should be utilized to search for new small molecules for SCD, using well-designed assays focused on several aspects of the phenotype. More about this and related NIH Roadmap activities is available at www.nihroadmap.nih.gov.

Among diverse points raised by various participants in the ensuing concluding discussion were:

  • What needs to be added?
    • Noninvasive imaging procedures
    • Lessons from other fields
    • A look at outliers in severity, including discordant sib pairs
    • Is this the time to explore regulatory networks and signaling pathways in SCD?
    • A global approach should be applied to issues such as to globin-switching, rather than simply utilizing only currently established researchers
  • There are informative models extant for getting information to communities.
  • For genetic counseling in general and preimplantation genetic diagnosis (PGD) in particular, we need to know more about perceptions of disease in SCD and the cultural competence of providers.
  • Patient advocacy and other community organizations used to see research as competing with community based resources for support; now that seems to be changing. The Sickle Cell Disease Association of America (SCDAA) is a potential advocate for research and research support, but has had a relatively modest impact on research, per se, in the past. The history in this field does raise important issues.
  • Innovative trans-agency participation is needed.
  • Economic status is an important factor in phenotypic variation in SCD, both in the U.S. and globally. This needs to be recognized in both research and clinical care.
  • Pain management in SCD and other quality of care issues are important.
  • Historically, SCD Centers have had to compete against each other for funding, which works against cooperative, multi-center projects. Current funding has moved in the direction of encouraging cooperation, but this needs to be further emphasized.
  • While there may be lessons to be learned from other organizations, the cystic fibrosis and SCD communities differ and lessons from the experience of one are not always directly applicable to the other.
  • There is a real opportunity for an international approach.
  • There is a need for leadership, both from NIH and within the SCD research community.
 

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Last Reviewed: March 26, 2014