FDA’s giant NMR magnet puts more imaging power into our regulatory science

By: Carolyn A. Wilson, Ph.D.

Carolyn A. WilsonThe word spin might make you think of someone trying to influence your opinion. But in physics, spin refers to an intrinsic property of certain subatomic particles that make some nuclei act like small magnets. That kind of spin is key to a powerful laboratory technique scientists use to study complex, carbon-based biological products at the atomic and molecular level.

This technique, called nuclear magnetic resonance (NMR), uses a strong, external magnetic field and radio waves to trigger the release of electromagnetic energy from atoms with nuclei that have spin. Computers convert these data into contour plots that resemble topographic land maps. Scientists use these data to determine the locations of atoms in relation to each other in molecules. This enables them to create three-dimensional models they can hold in their hands and study, or 3D images they can rotate on a computer screen.

Scientists in FDA’s Center for Biologics Evaluation and Research (CBER) are using NMR to study two types of molecules relevant to the vaccines against bacterial and viral disease that we regulate: polysaccharides (long chains of sugar molecules), which occur in either the cell wall or the capsule surrounding some disease-causing bacteria, and shorter chains of sugars called oligosaccharides. Oligosaccharides are found in viruses and are also part of bacterial vaccines.

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Scientists at FDA discuss construction of the facility that will house the new NMR. From left to right: Hugo F. Azurmendi (CBER), Kang Chen (CDER), Darón I. Freedberg (CBER) & Marcos D. Battistel (CBER). Get this and other FDA photos on Flickr.

The microbes need these molecules to cause disease, so CBER scientists are using NMR to study how the structure of such polysaccharides and oligosaccharides triggers production of antibodies against the microbes that carry these molecules. The methods developed by CBER scientists will allow evaluation of licensed and investigational polysaccharide vaccines by using NMR to determine if those vaccines were developed in a manner consistent with these insights into how the structure of these molecules triggers antibody production. In addition, the outcomes of these studies might provide information that manufacturers could use to design novel polysaccharide vaccines that are safe and effective.

Insights into the structures of polysaccharides that play critical roles in generating protective immune responses would be especially useful in confronting dangerous pathogens for which there are no vaccines. Two such pathogens, the bacteria Neisseria meningitidis B and Escherichia coli K1, cause meningitis (a potentially fatal inflammation of the brain and spinal cord). The capsules surrounding these bacteria contain a polysaccharide called polysialic acid. This molecule is unusual because it doesn’t trigger antibody production when injected by itself into adult humans, but people infected with bacteria that have polysialic acid in their cell walls or capsules do produce antibodies against it. One logical explanation for this difference is that “free” polysialic acid has a somewhat different structure than polysialic acid on bacterial cell walls. But, using NMR, CBER scientists found that polysialic had the same structure whether free or as part of the pathogen. Figuring out why only bound polysialic acid triggers antibody production might help researchers develop much needed vaccines for these bacteria. Soon they will have a new NMR facility at the White Oak campus that could help them solve that puzzle.

NMR "Stick" Model; NMR studies at CBER are providing insights into the atomic and molecular ins and outs of polysialic acid, a molecule found on the surface of bacteria, including some that cause meningitis. This work is aimed at helping researchers develop safe and effective vaccines against such bacteria that are based polysialic acid. Using the NMR data from their studies, the CBER scientists created two models of polysialic acid, a “stick” model and a “solid spheres” model, shown in the two short animated videos (above and below).

NMR “Stick” and “Solid Spheres” Models: NMR studies at CBER are providing insights into the atomic and molecular ins and outs of polysialic acid, a molecule found on the surface of bacteria, including some that cause meningitis. This work is aimed at helping researchers develop safe and effective vaccines against such bacteria that are based polysialic acid. Using the NMR data from their studies, the CBER scientists created two models of polysialic acid, a “stick” model (above) and a “solid spheres” model (below), shown in these two short animations.

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NMR “Solid Spheres” Model

The NMR spectrometer in the new facility will have a magnet that is much stronger than those previously used at FDA. The stronger the magnet, the more precise the data generated by NMR and the more precise the models that can be developed from this data.

To put this into perspective, the clinical application of NMR, called magnetic resonance imaging (MRI), uses magnets with strengths of 1.5 to 3 units of magnetic power called Tesla. The strength of NMR magnets at CBER is now about 16.4 Tesla (700 megahertz). The new NMR facility at White Oak will have a strength of 19.9 Tesla (850 megahertz)—about 6 times that of hospital MRI machines. In fact, the magnet is so powerful that the machine is isolated in a special room with walls thick enough to block its magnetic field from pulling unsecured metallic objects toward it. In the photograph you can see the NMR team visiting the facility as it is being prepared for the arrival of the machine.

CBER will share the new NMR spectrometer with the Center for Drug Evaluation and Research (CDER), which will use it to do extremely sensitive assessments of the purity of heparin and of the structures and properties of protein therapeutics.

This powerful magnetic molecular “microscope” is one way that FDA incorporates new technology into its regulatory science work to protect and promote the nation’s health.

Carolyn A. Wilson, Ph.D., is Associate Director for Research at FDA’s Center for Biologics Evaluation and Research.

FDA’s multi-pronged approach helps meet the challenge of bringing new and innovative antibiotics to patients who need them

By: Edward M. Cox, MD, MPH

With a growing number of infections becoming increasingly resistant to our current arsenal of antibiotics, developing new antibiotics to treat serious or life-threatening infections has become a key priority.

Edward Cox interview

There are significant scientific and economic challenges inherent to the development of new antibiotics. From a scientific standpoint, many patients with bacterial infections are often very sick and need to begin antibiotic therapy immediately, without further complications that enrollment in a clinical trial might involve. Moreover, it can be difficult to conduct a clinical trial involving very sick patients.

From an economic standpoint, antibiotics may be perceived as less potentially profitable for a company because they are generally taken only for a short period of time and often only for one course of treatment, by any given patient. Compare this to the long, dependable income stream from a diabetes medicine or a blood pressure medicine that a patient takes indefinitely, often for the rest of their life. These economic realities, which are rooted in the biology of acute bacterial infections, can make it challenging for a company to justify large expenditures for the development of drugs in this area, as a recent report by Eastern Research Group (ERG) affirms.

Provisions in a law passed a little over two years ago, commonly known as the GAIN Act, or the Generating Antibiotics Incentives Now Act, is helping to stimulate the development of new antibiotics. Under GAIN, certain antibacterial or antifungal drugs intended to treat serious or life-threatening infections can be designated “Qualified Infectious Disease Products” (QIDPs). As part of its QIDP designation, a drug receives priority review and can also receive fast track designation at the sponsor’s request. At the time of approval, a product with QIDP designation may be eligible for an additional five years of marketing exclusivity, exclusive marketing rights without competing with a generic drug product. To date FDA has granted 52 QIDP designations to 35 different unique molecules. We are already beginning to approve new antibacterial drugs with this beneficial QIDP designation.

FDA is working hard to streamline requirements for clinical trials for studying new antibacterial drugs and the provisions of the GAIN act are being actively implemented, but more is needed. There are still significant economic and scientific challenges in the development of new antibacterial drugs that need to be addressed. Additional financial incentives as well as new approaches for studying antibacterial drugs such as common clinical trial protocols could provide other important means to stimulate antibacterial drug development. We also need cutting-edge science to stimulate the development of new and innovative antibacterial drugs. To help drive this effort, FDA has assembled our Antibacterial Drug Development Task Force, a group of expert scientists and clinicians from within FDA, to consider opportunities to promote antibacterial drug development.

To advance this field, our Task Force is working with many leaders including those drawn from academia, regulated industry, professional societies, patient advocacy groups and government agencies. For example, FDA has contributed to the efforts of the Biomarkers Consortium of the Foundation for the National Institutes of Health to develop new endpoints for studying antibacterial drugs. FDA also works closely with the Clinical Trials Transformation Initiative (CTTI), a key group of dedicated scientists focused on advancing clinical trials for more efficient drug development. As a result, FDA and CTTI have helped convene a variety of important scientific meetings and activities on vital topics related to efficient clinical trial designs for testing new antibiotics. Our Task Force has also helped FDA team up with colleagues at the Brookings Institution’s Engelberg Center for Health Care Reform to help galvanize the scientific community’s efforts in new antibiotic drug development. August, 2012 began the first Brookings Council for Antibacterial Drug Development (BCADD) meeting, with meetings that occur approximately twice a year.

FDA and our Task Force members have also been busy on our own.  In February of 2013 we held a public meeting focused on creating an alternative approval pathway for certain drugs, such as antibacterial drugs, that are intended to address unmet medical need. We have also asked the public for their thoughts; in March of 2013, we issued a Federal Register Notice seeking input from the public on a wide range of topics related to antibacterial drug development. FDA has generated a number of guidance documents for industry, in draft and final form, that describe FDA’s scientific thinking with regard to developing new antibacterial drugs.

As part of our Task Force’s collaborative efforts, FDA is working closely with The National Institutes of Health (NIH) to further advance the development of new antibacterial drugs. Together, we are hosting a two-day Public Workshop to identify strategies for promoting clinical trials for antibacterial drugs and encouraging partnerships to accelerate their development. The ERG report will be presented at the workshop and other specific issues will be discussed including:

  • Priorities and strategic approaches to conducting clinical trials for antibacterial drugs
  • Regulatory pathways—including streamlined development programs for antibacterial drugs for patients with limited or no treatment options
  • Clinical trial design issues such as the development of common clinical protocols; using common control groups; statistical analysis issues; sharing data across trials (and data standards); appropriate clinical trial endpoints; and lessons learned from other therapeutic areas
  • The role of public-private partnerships in advancing the scientific and clinical trials enterprises

The work of the FDA Task Force as well as the GAIN Act have provided good first steps toward strengthening the antibacterial drug pipeline, but as the findings from the ERG report indicate, the forecast for antibacterial drug development likely will include a less than robust pipeline. Thus, additional attention on both financial incentives, new approaches for studying antibacterial drugs such as common protocols, as well as streamlined development pathways, likely will be needed to improve the climate.

Edward M. Cox, MD, MPH, is Director, Office of Antimicrobial Products, in FDA’s Center for Drug Evaluation and Research