Guidance for Industry
Prussian Blue Drug Products
 Submitting a New Drug
Application 
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
January 2003
Clinical Medical Guidance for Industry
Prussian Blue Drug Products
 Submitting a New Drug
Application
Additional copies are available from:
Division of Drug Information, HFD-240
Center for Drug Evaluation and Research
Food and Drug Administration
5600 Fishers Lane
Rockville, MD  20857
(Tel) 301-827-4573
 http://www.fda.gov/cder/guidance/index.htm
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
January 2003
Clinical Medical TABLE OF CONTENTS
I. INTRODUCTION.................................................................................................................1
II. BACKGROUND...................................................................................................................1
III. NDAs SUBMITTED FOR PRUSSIAN BLUE DRUG PRODUCTS...............................2
A. Types of NDAs for Prussian Blue.................................................................................................2
1. Submitting 505(b)(2) Applications...................................................................................................2
2. Submitting 505(b)(1) Applications...................................................................................................3
B. Content of NDAs for Prussian Blue..............................................................................................3
1. Chemistry, Manufacturing, and Controls Information....................................................................3
2. Labeling for Prussian Blue..............................................................................................................3
3. Patent Information...........................................................................................................................4
C. Exclusivity.......................................................................................................................................4
1. Five-Year Marketing Exclusivity.....................................................................................................5
2. Three-Year Exclusivity.....................................................................................................................5
3. Orphan Drug Exclusivity.................................................................................................................6
4. Waiver of Exclusivity.......................................................................................................................6
D. Innovative Prussian Blue Drug Products.....................................................................................6 Contains Nonbinding Recommendations
1
Guidance for Industry
Prussian Blue Drug Products  
Submitting a New Drug Application
This guidance represents the Food and Drug Administration's (FDA's) current thinking on this
topic.  It does not create or confer any rights for or on any person and does not operate to bind
FDA or the public.  An alternative approach may be used if such approach satisfies the
requirements of the applicable statutes and regulations.
I. INTRODUCTION
This guidance is intended to assist manufacturers wishing to submit new drug applications
(NDAs) for prussian blue drug products for the treatment of internal contamination with
radioactive thallium, nonradioactive thallium, or radioactive cesium.  The Federal Register
notice announcing the availability of this guidances explains in detail the Agency's findings
regarding safety and effectiveness and includes a list of the literature on which it based those
findings. 
II. BACKGROUND
Prussian blue was first synthesized in 1704 by a Berlin color maker named Diesbach.  It is used
as an industrial and artists' pigment.2   Since the 1960s, prussian blue also has been used
investigationally as an orally ingested drug to enhance the excretion of isotopes of cesium and
thallium from the body by means of ion exchange.  Prussian blue has a very high affinity for
cesium and thallium.  Cesium and thallium ions are ordinarily excreted into the intestine,
reabsorbed from there into the bile, and then excreted again into the gastrointestinal tract.  Orally
administered prussian blue traps thallium or cesium in the intestine, interrupts its reabsorption
                                                
1 This document was developed in the Division of Medical Imaging and Radiopharmaceutical Drug Products in the
Center for Drug Evaluation and Research (CDER), Food and Drug Administration (FDA).
2 The chemical name for prussian blue is ferric hexacyanoferrate(II).  The name prussian blue has been used for
various different, but chemically related, compounds used as a blue pigment.  However, for purposes of this notice
prussian blue refers only to insoluble ferric hexacyanoferrate (II), which has an empirical formula of Fe [Fe(CN) ]
4 6 3
and the Chemical Abstracts Service (CAS) registry number 14038-43-8.
1 Contains Nonbinding Recommendations
from the gastrointestinal tract, and thereby increases fecal excretion of thallium and cesium.
Prussian blue itself is not absorbed across the intestinal wall in significant amounts.3
The Agency has concluded that prussian blue, when produced under conditions specified in
approved NDAs, can be found to be safe and effective for the treatment of internal contamination
with radioactive thallium, nonradioactive thallium, or radioactive cesium.  As described below,
our conclusion is based upon our review of published information.  
III. NDAs SUBMITTED FOR PRUSSIAN BLUE DRUG PRODUCTS
A. Types of NDAs for Prussian Blue
An NDA for a prussian blue drug product may be either:
  a 505(b)(2) application, which is an NDA in which you rely for approval on studies that
you did not conduct, that were not conducted for you, or for which you do not have a
right of reference (described in section 505(b)(2) of the Federal Food, Drug, and
Cosmetic Act (the act) (21 U.S.C. 355(b)(2)) 
or
  a 505(b)(1) application, an NDA that relies exclusively on studies that you conducted,
that were conducted for you, or for which you have a right of reference (submitted under
section 505(b)(1) of the act. 
After an NDA for a prussian blue drug product has been approved, abbreviated new drug
applications (ANDAs) that refer to the approved prussian blue drug product can be submitted
and approved (see 21 CFR part 314, subpart c).  Because ANDAs cannot be submitted until an
NDA is approved, we primarily discuss 505(b)(1) and 505(b)(2) applications in this guidance.
1. Submitting 505(b)(2) Applications
If you rely on published literature, including the literature we have already reviewed (see the
Federal Register notice announcing the availability of this guidance) for approval of your
application, your NDA will be a 505(b)(2) application.  
A 505(b)(2) application could be considered the more direct and, probably, the quickest
approach to gaining approval of an NDA for a prussian blue drug product.  A 505(b)(2)
application could rely entirely on the published literature that we have already reviewed for the
clinical data required for approval of an NDA (see Federal Register notice).  If you took this
approach to approval, you would not need to submit copies or summaries of the reports we have
                                                
3 Prussian blue, in 500-milligram (mg) capsules, has been distributed by the Radiation Emergency Assistance
Center/Training Site (REAC/TS) under investigational new drug application (IND) number 51,700.  REAC/TS is
part of the Oak Ridge Associated Universities(ORAU). ORAU operates the Oak Ridge Institute for Science and
Education (ORISE) under a contract with the Department of Energy.  ORISE owns the IND for prussian blue.  The
500-mg capsules used under the IND are manufactured by HEYL Chemisch-pharmazeutische Fabrik GmbH & Co.
KG (HEYL).  HEYL uses the trade name Radiogardase-Cs for its 500-mg capsules of prussian blue.
2 Contains Nonbinding Recommendations
cited.  The clinical sections of your NDA would only have to cite the Federal Register notice and
the listed reports we relied on in making our determination of safety and effectiveness. 
2. Submitting 505(b)(1) Applications
As mentioned above, you can also submit a 505(b)(1) application.  This type of NDA relies only
on studies that you conducted, that were conducted for you, or for which you have a right of
reference.  These NDAs are sometimes called full NDAs and are the type of application most
frequently used to gain approval for drug products whose active ingredient is not in a previously
approved drug product.  
We recognize the importance of continuing the development of products, such as prussian blue,
to treat or prevent radiation and other types of toxicity.  We also recognize that you might not be
able to conduct definitive human efficacy studies for prussian blue because it would be unethical
to deliberately expose healthy human volunteers to a lethal or permanently disabling toxic
substance, and new field trials to study prussian blue's efficacy after an accidental or hostile
exposure to cesium-137 or thallium might be infeasible.  We encourage persons who wish to
submit 505(b)(1) applications for prussian blue drug products to contact us, before starting any
studies, to discuss the development of data to establish safety and effectiveness.
B. Content of NDAs for Prussian Blue 
NDAs submitted to the Agency for approval must include chemistry, manufacturing, and
controls information.  They must also contain labeling and the appropriate patent information.
These requirements are contained primarily in ' 314.50 (21 CFR 314.50).
1. Chemistry, Manufacturing, and Controls Information 
In addition to the clinical data discussed in the Federal Register notice announcing the
availability of this guidance and in section 1.A.2 of this guidance, your NDA must also include a
complete chemistry, manufacturing, and controls section describing the composition,
manufacture, and specification of the drug substance and drug product (section 355(b)(1) of the
act and ' 314.50).  You also must meet all other applicable requirements regarding the content of
an NDA (section 355(b)(1) of the act and ' 314.50).
HEYL's 500-mg prussian blue capsules were used in the majority of the recent published studies.
If you rely on the published literature we reviewed in making our determination about the
potential safety and effectiveness of prussian blue, you should submit the results of in vitro
studies showing that your product's binding to thallium and nonradioactive cesium is comparable
to that of HEYL's product.
2. Labeling for Prussian Blue
We have prepared draft labeling for orally administered drug products containing 500-mg
prussian blue capsules.  You can use this labeling for drug products as part of a 505(b)(2)
application for 500-mg prussian blue capsules.  This draft labeling reflects our conclusion on the
3 Contains Nonbinding Recommendations
potential safety and effectiveness of 500-mg prussian blue drug products for treatment of internal
contamination with radioactive thallium, nonradioactive thallium, or radioactive cesium.  If you
wish to change the labeling to include a different or broader indication, different dosage, or make
any other significant changes to the draft labeling, you should provide, as part of your 505(b)(2)
application, additional literature or other studies to support your requested changes.  If you
submit a 505(b)(1) application for a prussian blue drug product, you cannot use this labeling
because it is based on our review of the published literature.  If you submit a 505(b)(1)
application for prussian blue, your labeling must be based on the data contained in your NDA
(section 355(b)(1) of the act and  314.50).  
The draft labeling for 505(b)(2) applications is available on the Internet.4  You may also contact
the Center for Drug Evaluation and Research's Division of Medical Imaging and
Radiopharmaceutical Drug Products for a copy of the draft labeling.
3. Patent Information 
If you submit an NDA (including a 505(b)(2) NDA) for prussian blue, you must file with your
NDA a list of the patent numbers and expiration dates for each patent required to be submitted
under section 355(b)(1)(F) of the act and  314.50.  You also must submit additional patent
information within 30 days of approval of your NDA or, in the case of newly issued patents,
within 30 days of issuance of the patent (section 355(c)(2) of the act and  314.50).  If your NDA
is approved, we will publish the patent information in "Approved Drug Products with
Therapeutic Equivalence Evaluations" (the Orange Book). 
We publish information regarding patents and exclusivity periods for approved drug products in
the Orange Book.  This information is important if you are considering submitting ANDAs or
505(b)(2) applications for prussian blue drug products.  If a drug product listed in the Orange
Book has listed patents, the 505(b)(2) application or ANDA seeking to rely on the finding of
safety or effectiveness for that listed drug must contain certifications regarding those patents (see
' 314.50(i) for 505(b)(2) applications, and  314.94(a)(12) for ANDAs). 
C. Exclusivity
In addition to the protection provided by patents issued by the U.S. Patent and Trademark Office,
prussian blue drug products approved by us may be protected from competition by periods of
marketing exclusivity that are administered by us.  The act provides for periods of marketing
exclusivity that prevent us from filing or approving 505(b)(2) applications or ANDAs for drug
products that contain the same active moiety5 as certain previously approved drug products.  The
active moiety of a prussian blue drug product would be the prussian blue molecule (i.e., the ferric
hexacyanoferrate (II) molecule).  
                                                
4 See http://www.fda.gov/cder/foi/label/2003/ind51700lbl.pdf.
5 Active moiety is defined in 21 CFR 314.100(a) as the molecule or ion, excluding those appended portions of the
molecule that cause the drug to be an ester, salt (including a salt with hydrogen or coordination bonds), or other
noncovalent derivative (such as a complex, chelate, or clathrate) of the molecule, responsible for the physiological
or pharmacological action of the drug substance.
4 Contains Nonbinding Recommendations
The following summaries of marketing exclusivity and orphan drug exclusivity are provided
solely for the general information of manufacturers considering submitting an NDA for a
prussian blue drug product.  They should not be read as statements of our general policies
regarding marketing exclusivity and orphan drug exclusivity.  Our policy can be found in the
regulations cited in this guidance. 
 
1. Five-Year Marketing Exclusivity
A 5-year period of marketing exclusivity is provided by section 505(c)(3)(D)(ii) and (j)(5)(D)(ii)
of the act when a sponsor obtains approval of an NDA for which no active moiety has been
previously approved by the FDA.  The 5-year period of marketing exclusivity generally prohibits
us from filing a 505(b)(2) application or receiving an ANDA for a drug product that contains the
same active moiety as the first drug product containing the active moiety to be approved.6  The
5-year period of marketing exclusivity begins on the approval date of the first NDA approved for
a drug product containing the active moiety.  Both 505(b)(1) and 505(b)(2) applications may be
entitled to benefit from 5-year marketing exclusivity, but only 505(b)(2) applications and
ANDAs are blocked by 5-year marketing exclusivity.
Because we have never approved a drug product that contains the prussian blue molecule as the
active moiety, the first NDA approved that contains prussian blue as the active moiety will likely
receive 5 years of marketing exclusivity. If 5-year exclusivity is awarded for an NDA containing
prussian blue, we cannot file7 a subsequent 505(b)(2) application for 5 years after the approval
date of that NDA.  If you have submitted an essentially complete 505(b)(2) application before we
approve the first NDA for a prussian blue drug product, review and approval of your 505(b)(2)
application would not be blocked by the marketing exclusivity obtained by the first prussian blue
drug product approval (54 FR 28872 at 28901, July 10, 1989).  However, after we have approved
the first NDA for prussian blue, 5-year marketing exclusivity would prohibit us from filing your
505(b)(2) application, no matter how soon after the first approval we received your application. 
2. Three-Year Exclusivity
A 3-year period of marketing exclusivity may be applicable to prussian blue drug products
sometime in the future.  Three-year marketing exclusivity is provided by section
505(c)(3)(D)(iii) and (j)(5)(D)(iii) of the act.  Drug products whose active moiety is the same
active moiety as that in a previously approved drug product are entitled to 3-year exclusivity if a
new clinical study (other than a bioavailabilty or bioequivalence study) is needed for their
approval.  If a drug product, or change to a drug product, is given 3 years of exclusivity, we are
barred for 3 years from approving any 505(b)(2) application or ANDA for the same drug
product, or change to the product, that was granted exclusivity.  For example, if an applicant
obtains 3 years of exclusivity for a new dosage form of prussian blue, FDA may not approve a
505(b)(2) application or an ANDA for that dosage form of prussian blue for 3 years.  However,
                                                
6 An exception to the 5-year period permits an applicant to submit a 505(b)(2) application or ANDA after 4 years if
it contains a certification of invalidity or noninfringement for a patent listed for the approved drug.
7  Our regulations regarding filing an NDA and receiving an ANDA are found at 21 CFR 314.101.
5 Contains Nonbinding Recommendations
we can approve a 505(b)(2) application or an ANDA for any previously approved dosage form
not protected by the exclusivity.  
Our regulations in  314.108 provide more details on marketing exclusivity.  If you are interested
in how marketing exclusivity could affect your NDA for prussian blue, you are encouraged to
discuss the issue with the Center for Drug Evaluation and Research's Division of Medical
Imaging and Radiopharmaceutical Drug Products.  If you believe your drug product is entitled to
marketing exclusivity, you must submit supporting information in your NDA (' 314.50(j)).
3. Orphan Drug Exclusivity
In addition to 3- or 5-year marketing exclusivity, orphan drug exclusivity may apply to prussian
blue drug products approved for orphan indications.  Obtaining orphan drug exclusivity is a two-
step process.  The regulations require that you seek orphan drug designation for the active moiety
of your drug product for an orphan indication before you submit an NDA.  If we designate the
drug as an orphan drug and then approve it for the designated indication, the drug will receive
orphan drug exclusivity.  The issues involved in determining which drug products are entitled to
orphan drug exclusivity and which drug products are blocked by orphan drug exclusivity are
described in our regulations in part 316 (21 CFR part 316).  However, we note that orphan drug
exclusivity is for a 7-year period and can prohibit us from approving a 505(b)(1) application, a
505(b)(2) application, or an ANDA for the same active moiety for the same indication during the
period of exclusivity.  This differs from 5-year marketing exclusivity, which prohibits us from
filing a 505(b)(2) application or receiving an ANDA, but would not prohibit us filing a 505(b)(1)
application. 
4. Waiver of Exclusivity
If your right to any type of exclusivity for a prussian blue drug product has vested, you can
waive that exclusivity.  Your waiver would allow one or more applicants to submit applications
for the product.  For example, if you obtain 5-year exclusivity with a 505(b)(2) application for a
prussian blue drug product, your complete waiver of such exclusivity would enable other
applicants to immediately submit 505(b)(2) applications and ANDAs for drug products
containing prussian blue.  
D. Innovative Prussian Blue Drug Products
We encourage the development of drug products containing prussian blue for the treatment of
internal contamination with radioactive thallium, nonradioactive thallium, or radioactive cesium
that represent improvements in safety, effectiveness, or convenience.  However, your submission
of a 505(b)(2) application for such an innovative product may be blocked by marketing
exclusivity if the exclusivity is not waived.  If the innovative product is clinically superior to the
previously approved drug product, its approval might not be blocked by orphan drug exclusivity
(see ' 316.3(b)(13)).  Once approved, an innovative product may qualify for 3-year marketing
exclusivity.  If the innovation presents a commercial advantage over the drug product that enjoys
marketing exclusivity, it may be possible to reach an agreement with the person holding the
exclusivity to allow marketing of the innovative drug product.
6