Conditions: Depression
Keywords: Healthy Control Subjects PET Imaging Receptor Occupancy Depression
Allocation: NON_RANDOMIZED | Intervention model: SINGLE_GROUP
Enrollment: 3
Healthy volunteers: yes

Brief summary:
Background:

The brain enzyme phosphodiesterase-4D (PDE4D) may affect thinking and depression. Drugs with some radioactivity can attach to enzymes and be seen on a scan. Researchers want to test a new radioactive drug, 11C-T-1650, to measure PDE4D in the brain and body. They also want to see if the new drug BPN14770 blocks 11C-T-1650 from the brain. They want to learn more about psychiatric disorders and possible treatments.

Objectives:

To study how well 11C-T-1650 helps show PDE4D on a scan and to see if BPN14770 blocks it.

Eligibility:

Healthy adults at least 18 years old

Design:

Participants will be screened in other protocols.

Some participants will have 1 body PET scan.

Some participants will have 2 brain PET scans and 1 brain MRI within 1 year.

Some participants (ages 18 55) will:

Have 3 brain PET scans and 1 MRI

Take BPN14770 by mouth twice daily for 3 7 days

Have blood and urine tests

Have a follow-up physical exam and heart test

PET (positron emission tomography) scans will take 2 3 hours. Participants will:

Have a thin plastic tube (catheter) placed in an arm vein by needle.

Get a small amount of 11C-T-1650 injected via catheter. Another catheter may be placed to draw blood.

Lie quietly on a bed that slides into a donut-shaped scanner without sleeping. They may get a short break.

Have heart and vital signs monitored.

Have blood and urine tests.

Learn about drinking fluids and urinating after the scan

MRI (magnetic resonance imagining) scans will take 30 60 minutes:

Participants will lie on a table that slides into a metal cylinder in a magnetic field.

Sponsoring Institute: National Institute of Mental Health

...

Detailed description:
Objective

Phosphodiesterase type 4 (PDE4) metabolizes 3 \<=,5 \<=-cyclic adenosine monophosphate (cAMP), thereby terminating this second messenger. PDE4 is selective to cAMP over cyclic guanosine monophosphate. PDE4 has four isozymes A, B, C, and D and basic studies suggest that type D (PDE4D) may play a key role in cognitive function and depression. That is, PDE4D inhibitors are expected to improve cognitive function and depressive symptoms.

In collaboration with Tetra Discovery Partners, we have developed a PET ligand, 11C-T-1650, to selectively image PDE4D. This type D selective ligand was developed based on 3D structural differences between PDE4D and PDE4 type B (PDE4B) Our PET studies using 11C-T-1650 in nonhuman primate have shown promising results, and we now seek to evaluate it in in healthy subjects.

This study has three primary objectives. First, we will determine whether the uptake of 11C-T-1650 in the brain reflects the distribution of PDE4D, as demonstrated by blocking with a PDE4D selective compound BPN14770, being developed by Tetra Discovery Partners for treating cognitive disorders including depression. Second, we will measure binding site occupancy of BPN14770 administered at doses that may be used in clinical trials. Third, we will measure the test/retest reproducibility of brain uptake quantified by kinetic modeling and using arterial blood samples.

Study Population

Healthy adult female and male volunteers (age greater than or equal to 18) will have either brain (n = 30) or whole body imaging (n = 10).

Design

* Phase 1: We will begin with whole body scanning in a single human subject using up to 10 mCi 11C-T-1650 The aim of this first scan will be to detect a tracer that disproportionately accumulates in a single radiosensitive organ, such as the gonads. If we confirm that radioactivity is fairly widely distributed in the body, higher activities may be injected.
* Phase 2: Fifteen healthy subjects will have three brain PET scans using 20 mCi of 11C-T-1650. Scan 1 will serve as the baseline scan for comparison to enzyme occupancy studies (Scan 2 and - Scans 2 and 3 will be enzyme occupancy studies using the PDE4D selective medication BPN14770.Scans 2 and Scan 3 will be performed approximately 90-180 min after the first dose of BPN14770 and after three-day administration, respectively. Scan 3 will be performed approximately 90-180 min after the last dose of the three-day administration of BPN14770. The dose of BPN14770 is 50 mg BID for three days, and a single dose on the fourth day. Comparison between Scan 1 and 2 provides accurate measurement of nonspecific binding of 11C-T-1650. Comparison between Scan 1 and 3 provides enzyme occupancy at a stable plasma concentration of BPN14770 based on Phase 1/2 clinical trials performed by Tetra Discovery Partners. Blood samples will be measured for BPN14770 levels.
* Phase 3: To obtain dosimetry information, we will perform a whole body PET scan using 11C-T-1650 (20 mCi) in up to nine healthy subjects.
* Phase 4: Fifteen healthy subjects will have two brain PET scans using 20 mCi of 11C-T-1650 to study test/retest reproducibility of the PET measurement. BPN14770 will not be administered in Phases 1, 3 or 4.

Outcome Measures

For whole body imaging, organ uptake will be quantified as a Standardized Uptake Value (SUV), which normalizes for injected activity and body weight. For Scan 1 and 2 of Phase 2 and all scans of Phase 4, uptake will be quantified as total distribution volume (VT) calculated with kinetic modeling and serial concentrations of parent radioligand in arterial plasma. For Scan 3 of Phase 3, brain uptake (SUV) normalized to plasma concentrations of 11C-T-1650 will be used to measure radioligand binding because the interval between Scan 2 and 3 is too short to repeat placing arterial line. From VT or normalized SUV, occupancy of BPN14770 and nonspecific binding of 11C-T-1650 will be measured. Occupancy of PDE4D will be compared to blood levels of BPN14770.

Arms:
arm 1: 10 mCi of 11C-T-1650 given intravenously once followed by a Whole Body PET scan. This was done for whole body dosimetry calculations. arm 2: Baseline brain PET scan (scan 1) with 20 mCi of 11C-T-1650 given intravenously, followed by a second Brain PET scan (scan 2) 90-180 minutes after first dose administration of BPN14770 50mg given orally. A third brain PET scan (scan 3) is performed after the last dose of BPN14770. 20 mCi of 11C-T-1650 is given intravenously with each PET scan. BPN14770 50mg given orally twice a day for a total of seven doses. BPN14770 is a PDE4D-inhibitor.

Interventions: intervention 1: [C-11]T-1650 intervention 2: BPN14770
Intervention descriptions: intervention 1: radio-labeled drug intervention 2: selective compound

Protocol document:
Prot_SAP_000.pdf: 
 
CNS IRB Protocol Template (05.04.17) 
 
 
Protocol Title: Evaluation of a novel PET radioligand for phosphodiesterase-4D (PDE4D) 
Abbreviated Title: PET imaging of PDE4D 
Protocol Number: 19-M-0064 
Date of This Submission/Version: 4/3/19 
 
Principal Investigator 
Name, Degree 
Branch/Institute Bldg/Rm 
Phone 
E-mail 
Robert Innis, 
MD, PhD 
MIB/NIMH 
10/B1D43 
301-594-1368 
robert.innis@nih.gov 
 
Associate Investigators  
Name, Degree 
Branch/Institute Bldg/Rm 
Phone 
E-mail 
M. Desiree 
Ferraris Araneta, 
C-RNP 
MIB/NIMH 
10/B1D43 
301-496-9423 
ferrarism@mail.nih.gov 
Denise Rallis-
Frutos, DNP 
MIB/NIMH 
10/B1D43 
301-366-2503 
rallisd@mail.nih.gov 
 
 
 
 
 
Victorino, 
Milalynn 
NIMH 
10/B1D43 
301-451-7904 
victorinom@mail.nih.gov 
Lora Deuitch 
Weidner, PhD 
MIB/NIMH 
10/B1D43 
301-594-5721 
Lora.deuitch@nih.gov 
 
Referral Contact  
Name, Degree 
Branch/Institute Bldg/Rm 
Phone 
E-mail 
Holly A Giesen 
MIB/NIMH 
10/B1D43 
301-435-8982 
giesenh@mail.nih.gov 
 
 
Accountable Investigator 
Name, Degree 
Branch/Institute Bldg/Rm 
Phone 
E-mail 
Robert Innis, MD, 
PhD 
MIB/NIMH 
10/B1D43 
301-594-1368 
robert.innis@nih.gov 
 
Medical Advisory Investigator  
Name, Degree 
Branch/Institute Bldg/Rm 
Phone 
E-mail 
Robert Innis, MD, 
PhD 
MIB/NIMH 
10/B1D43 
301-594-1368 
robert.innis@nih.gov 
 
Human Research Protections Program Investigator and Staff Training: 
 
For this protocol, the following “just in time” human subjects protection training courses are 
required for investigators and staff: 
 NIAID GCP course or CITI GCP modules 
 Unanticipated Problems and Reporting Requirements in Biomedical Research 
 
Total requested accrual 
  (0) Patients       


 
 
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  (40) Healthy Volunteers  
 
  
 
Project Uses Ionizing Radiation:    No  
■ Yes (attach RSC/RDRC documentation) 
  
 
Medically-indicated only 
  
 
■Research-related only 
  
 
Both 
 
IND/IDE 
 
 
 
 No   
■ Yes (attach FDA documentation) 
  
Drug: 11C-T1650. Not yet submitted  
  
Sponsor: NIMH IRP  
 
  
Drug:  BPN14770: #127,905 
  
Sponsor: Tetra Discovery Partners, Grand Rapids, MI 
Durable Power of Attorney  
 
■ No   
 Yes  
 
Multi-institutional Project 
 
■ No   
 Yes  
 
 
 
 
 
Institution#1_________________    FWA #_________  
Date of IRB approval ______________(attach IRB documentation) 
 
 
 
Institution#2_________________    FWA #_________  
Date of IRB approval ______________(attach IRB documentation) 
 
Data and Safety Monitoring Board  
 No   
■ Yes  
 
Technology Transfer Agreement  
No   
■  Yes  
Agreement type and number _CTA_____ Expiration Date_01/27/2028_________ 
 
Samples are being stored  
 
 
■ No   
 Yes  
Covered protocol requiring  DEC approval No  
 
■  Yes 
Flesch-Kincaid reading level of consent forms:   
 Phase 1: 8.9 
 Phase 2: 8.7 
 Phase 3: 8.9 
 Phase 4: 8.7 
 
 


 
 
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Précis: 
i. 
Objective 
Phosphodiesterase type 4 (PDE4) metabolizes 3′,5′-cyclic adenosine monophosphate 
(cAMP), thereby terminating this second messenger. PDE4 is selective to cAMP over cyclic 
guanosine monophosphate. PDE4 has four isozymes—A, B, C, and D—and basic studies suggest 
that type D (PDE4D) may play a key role in cognitive function and depression. That is, PDE4D 
inhibitors are expected to improve cognitive function and depressive symptoms. 
In collaboration with Tetra Discovery Partners, we have developed a PET ligand, 11C-T-
1650, to selectively image PDE4D. This type D selective ligand was developed based on 3D 
structural differences between PDE4D and PDE4 type B (PDE4B) Our PET studies using 11C-T-
1650 in nonhuman primate have shown promising results, and we now seek to evaluate it in in 
healthy subjects. 
This study has three primary objectives. First, we will determine whether the uptake of 
11C-T-1650 in the brain reflects the distribution of PDE4D, as demonstrated by blocking with a 
PDE4D selective compound BPN14770, being developed by Tetra Discovery Partners for 
treating cognitive disorders including depression. Second, we will measure binding site 
occupancy of BPN14770 administered at doses that may be used in clinical trials. Third, we will 
measure the test/retest reproducibility of brain uptake quantified by kinetic modeling and using 
arterial blood samples. 
 
ii. 
Study Population 
Healthy adult female and male volunteers (age ≥ 18) will have either brain (n = 30) or whole   
body imaging (n = 10). 
 
iii. 
Design 
 
a) Phase 1: We will begin with whole body scanning in a single human subject using up to 
10 mCi 11C-T-1650 The aim of this first scan will be to detect a tracer that 
disproportionately accumulates in a single radiosensitive organ, such as the gonads. If we 
confirm that radioactivity is fairly widely distributed in the body, higher activities may be 
injected.  
 
b) Phase 2: Fifteen healthy subjects will have three brain PET scans using 20 mCi of 11C-T-
1650. Scan 1 will serve as the baseline scan for comparison to enzyme occupancy studies 
(Scan 2 and 3). Scans 2 and 3 will be enzyme occupancy studies using the PDE4D 
selective medication BPN14770.Scans 2 and Scan 3 will be performed approximately 90-
180 min after the first dose of BPN14770 and after three-day administration, respectively. 
Scan 3 will be performed approximately 90-180 min after the last dose of the three-day 
administration of BPN14770. The dose of BPN14770 is 50 mg BID for three days, and a 
single dose on the fourth day. Comparison between Scan 1 and 2 provides accurate 
measurement of nonspecific binding of 11C-T-1650. Comparison between Scan 1 and 3 
provides enzyme occupancy at a stable plasma concentration of BPN14770 based on 
Phase 1/2 clinical trials performed by Tetra Discovery Partners.  Blood samples will be 
measured for BPN14770 levels. 
 


 
 
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c) Phase 3: To obtain dosimetry information, we will perform a whole body PET scan using 
11C-T-1650 (20 mCi) in up to nine healthy subjects. 
 
d) Phase 4: Fifteen healthy subjects will have two brain PET scans using 20 mCi of 11C-T-
1650 to study test/retest reproducibility of the PET measurement. BPN14770 will not be 
administered in Phases 1, 3 or 4. 
 
 
iv. 
Outcome Measures 
For whole body imaging, organ uptake will be quantified as a Standardized Uptake Value 
(SUV), which normalizes for injected activity and body weight. For Scan 1 and 2 of Phase 2 and 
all scans of Phase 4, uptake will be quantified as total distribution volume (VT) calculated with 
kinetic modeling and serial concentrations of parent radioligand in arterial plasma. For Scan 3 of 
Phase 3, brain uptake (SUV) normalized to plasma concentrations of 11C-T-1650 will be used to 
measure radioligand binding because the interval between Scan 2 and 3 is too short to repeat 
placing arterial line. From VT or normalized SUV, occupancy of BPN14770 and nonspecific 
binding of 11C-T-1650 will be measured.  Occupancy of PDE4D will be compared to blood 
levels of BPN14770. 
 
 


 
 
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Table of Contents 
1. 
Introduction and Background .............................................................................................. 7 
2. 
Study Objectives ................................................................................................................ 18 
3. 
Subjects .............................................................................................................................. 18 
4. 
Study Design and Methods ................................................................................................ 20 
5. 
Management of Data and Samples .................................................................................... 26 
6. 
Additional Considerations ................................................................................................. 27 
7. 
Risks and Discomforts ....................................................................................................... 27 
8. 
Subject Safety Monitoring ................................................................................................. 30 
9. 
Outcome Measures............................................................................................................. 30 
10. 
Statistical Analysis ............................................................................................................. 31 
11. 
Human Subjects Protection ................................................................................................ 31 
12. 
Anticipated Benefit ............................................................................................................ 33 
13. 
Classification of Risk ......................................................................................................... 33 
14. 
Consent Documents and Process ....................................................................................... 33 
15. 
Data and Safety Monitoring ............................................................................................... 34 
16. 
Quality Assurance .............................................................................................................. 34 
17. 
Reporting of Unanticipated Problems, Adverse Events, and Protocol Deviations ............ 35 
18. 
Alternatives to Participation .............................................................................................. 35 
19. 
Privacy ............................................................................................................................... 36 
20. 
Confidentiality ................................................................................................................... 36 
21. 
Conflict of Interest ............................................................................................................. 36 
22. 
Technology Transfer .......................................................................................................... 36 
23. 
Research and Travel Compensation................................................................................... 36 
24. 
References .......................................................................................................................... 39 
25. 
Attachments ....................................................................................................................... 41 
26. 
Consent Forms ................................................................................................................... 41 
 
List of Abbreviations  
AUC  
area under the curve 
BID 
twice a day 
BPND 
Binding potential relative to nondisplaceable distribution volume, specific-to-
nondisplaceable ratio of distribution volume 
cAMP  
3′,5′-cyclic adenosine monophosphate 
MRI 
 
magnetic resonance imaging 
PDE4  
phosphodiesterase type 4 
PDE4D 
PDE4 subtype D 


 
 
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PET 
 
positron emission tomography 
SUV  
standardized uptake value 
BPND   
specific-to-nondisplaceable ratio of distribution volume 
VT  
 
total (specific plus nondisplaceable) distribution volume 
 
 


 
 
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1. Introduction and Background 
 
PDE4D inhibitors produce cognitive improvement and may show antidepressant effects 
 
PDE4 terminates signal transduction of G-protein-coupled receptors by metabolizing the 
second messenger cAMP. Because of the prevalence of G-protein-coupled receptors, PDE4 plays 
critical roles in a number of brain disorders including Alzheimer’s disease and major depressive 
disorder. 
 
A large number of pre-clinical and clinical trials have been performed using PDE4 
inhibitors. Uncontrolled clinical studies conducted in the late 1980s and early 1990s with 
rolipram, an isozyme nonselective PDE4 inhibitor, found that this agent had antidepressant 
effects; however, the ratio of efficacy to adverse reactions limited its clinical use [1]. Two 
possible causes have been hypothesized for the low ratio of efficacy to adverse reaction: little 
selectivity of rolipram among the four PDE4 isozymes [2] and high inhibition of PDE4 activity 
because rolipram is a competitive inhibitor [3]. Building on these hypotheses, PDE4D selective 
negative allosteric modulators have been developed which induced cognitive improvement 
without causing emesis [3]. Inhibition of PDE4D is also expected to show antidepressant effects 
because PDE4D KO mouse showed antidepressant-like effect on behavior [4] 
 
As described in the following subsections in detail, we have performed extensive studies 
using 11C-(R)-rolipram, which binds to all four PDE4 isozymes. To further investigate the role of 
PDE4 in brain disorders, a PET ligand that binds selectively to one of the four PDE4 isozymes is 
needed. Tetra Discovery Partners has developed a new PDE4D selective ligand, 11C-T-1650. We 
tested 11C-T-1650 in monkey PET studies and confirmed that specific binding of 11C-T-1650 is 
greater than that of 11C-(R)-rolipram, although T-1650 binds to only one subtype of PDE4 while 
rolipram binds to all subtypes. This specific binding suggests that 11C-T-1650 has much higher in 
vivo affinity than 11C-(R)-rolipram for PDE4. 
We will also measure the enzyme occupancy by doses of BPN14770 that might be used 
in clinical studies and relate this to plasma levels of the drug. If all studies proceed well, the 
results will be used to guide a therapeutic trial in major depressive disorder (MDD) to improve 
cognitive function and depressive symptoms. 
 
Previous PET studies using 11C-(R)-rolipram, a PDE4 isozyme nonselective inhibitor 
PET imaging of the cAMP cascade 
PET imaging of PDE4 with 11C-(R)-rolipram has been successfully used to study cAMP 
cascade activity in vivo. PDEs hydrolyze the second messengers cAMP and cyclic guanosine 
monophosphate (cGMP) to terminate signal transduction. Eleven PDEs exist in the human body. 
PDE4 is selective to cAMP and is present in both brain and peripheral organs such as heart, 
lungs, kidney [5], immune cells [6], osteoclasts [7], and osteoblasts [8]. Rolipram is a selective 
PDE4 inhibitor; PDE4 has four isozymes, and rolipram is not selective among these isozymes. 
Our studies—described below—demonstrated that 11C-(R)-rolipram PET is a valuable 
method for detecting cAMP cascade activity in living human and animal subjects. Because PDE4 
is present in almost all brain regions and no regions without PDE4 are available to use as a 
reference to measure rolipram binding, we used 11C-(R)-rolipram concentrations in arterial 
plasma (i.e., metabolite-corrected arterial input function) to measure rolipram binding in the 
brain [9, 10]. We also showed that rolipram binding can be accurately measured using only four 
arterial samples [9]. 


 
 
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Broadly, the cAMP theory of depression posits that depression is caused by low cAMP 
signaling. The corresponding theory regarding the relevant mechanism of treatment is that 
chronic, but not acute, administration of antidepressants upregulates cAMP signaling. Although 
the cAMP theory of depression has limited supporting data, evidence for the mechanism of 
antidepressants has repeatedly been confirmed in animal studies. Chronic, but not acute, 
administration of all classes of antidepressants, as well as electroconvulsive therapy, upregulates 
several components of the cAMP pathway, including PDE4. 
PDE4, an important component of the cAMP cascade, selectively metabolizes cAMP in 
the brain to the inactive monophosphate. Rolipram is a reversible inhibitor of PDE4, and binding 
of 11C-(R)-rolipram provides a measure of the activity of this enzyme in the brain. Due to a 
feedback mechanism, in vivo binding of 11C-(R)-rolipram reflects the activity of the cAMP 
cascade; essentially, increased cAMP stimulates protein kinase A (PKA), which phosphorylates 
PDE4 that, in turn, increases 
rolipram binding. 
We confirmed in animals 
that increased 11C-(R)-rolipram 
binding reflects the 
phosphorylated / active state of 
PDE4. Using this radioligand, 
we found that PDE4 binding is 
decreased in unmedicated 
patients with MDD, consistent 
with the cAMP theory of 
depression. Finally, we found 
that two months of treatment 
with an SSRI increased 
(normalized) PDE4 binding, 
consistent with the cAMP theory 
of the mechanism of 
antidepressants. 
In Vivo Density and 
Affinity. Our initial experiments 
sought to measure in vivo both 
binding site density and 
radioligand affinity of 11C-(R)-
rolipram in the rat brain [11]. We 
also studied two critical factors 
in small-animal PET scans: the 
influence of anesthesia and the 
difference in binding under in 
vivo and in vitro conditions. Binding site density and radioligand affinity of conscious rats were 
significantly greater than those of anesthetized rats, by 29% and 59%, respectively. In addition, 
in vitro affinity was five-fold greater than in vivo affinity, although density was similar in both 
conditions (Fig 1). The findings were consistent with rapid dephosphorylation of PDE4 and 
established that 11C-(R)-rolipram binding in vivo reflects cAMP cascade activity in rats.  
 
Fig 1. In vivo Scatchard plot of PDE4 binding using 11C-(R)-rolipram 
in awake rats. PET scans were performed with increasing 
concentrations of radioligand in order to saturate binding to PDE4 
(bottom left), and analyzed as an in vivo Scatchard plot (bottom right). 
The brains were subsequently harvested for in vitro Scatchard analysis. 
Binding density (Bmax) was unchanged, but binding affinity was 
decreased five- to six-fold after death compared to the awake 
condition. The decreased affinity after death is consistent with the 
rapid dephosphorylation (within minutes) of PDE4. The 
phosphorylation state of PDE4 would not be possible in human 
postmortem tissue; PET imaging is the only technique currently 
available to measure the phosphorylated and active state of this 
enzyme. 


 
 
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In Vivo Phosphorylation 
Status. We further examined the 
effects of PKA modulators in 
conscious rats on 11C-(R)-rolipram 
binding compared to the much 
less active enantiomer 11C-(S)-
rolipram (Fig 2) [12]. Two drugs 
were studied. db-cAMP, which is 
a cAMP analogue, was used to 
activate PDE4, thus increasing 
activity of the cAMP-dependent 
PKA. PKA then phosphorylated 
the PDE4 enzyme and increased 
PDE4 activity. We also studied 
Rp-cAMP, a PKA inhibitor that 
directly inhibits PKA function, 
thereby decreasing PDE4 activity. 
Unilateral injection of the PKA 
activator (db-cAMP) and the PKA 
inhibitor (Rp-cAMP) into the 
striatum significantly increased 
and decreased 11C-(R)-rolipram 
binding, respectively. These 
effects were not caused by 
changes in blood flow or delivery 
of radioligand to the brain, 
because these agents did not affect 
11C-(S)-rolipram binding. These results supported the importance of measuring in vivo 11C-(R)-
rolipram binding in the brain to assess response to physiological or pharmacological challenges 
to the cAMP second messenger system. 
 
Fig 2. 11C-(R)-rolipram binding in rat brain depends on the 
phosphorylation state of PDE4. Rats were unilaterally injected in 
striatum with either a PKA activator (db-cAMP, upper panels) or a 
PKA inhibitor (Rp-cAMPS, lower panels). PKA-mediated 
phosphorylation of PDE4 increased both enzyme activity and the 
affinity of 11C-(R)-rolipram binding about 10-fold. Both the PKA 
activator and inhibitor had the expected effect on radioligand uptake 
in striatum injected with drug compared to the side injected with 
saline. These effects were not merely caused by altered blood flow, 
given that they were not found using the inactive enantiomer 11C-(S)-
rolipram (right panels). 


 
 
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PDE4 Binding in MDD. Based on these preclinical findings, we hypothesized that 11C-(R)-
rolipram PET in humans would provide a unique in vivo measure of PDE4 density and affinity 
not possible in postmortem tissue. Expanding 
our work, we sought to quantify the binding 
of 11C-(R)-rolipram as an indirect measure of 
this enzyme’s activity in the brain of 
individuals with MDD compared with 
healthy controls [13]. This is particularly 
important because animal studies had 
suggested that upregulation of the cAMP 
cascade, including PDE4, was a mechanism 
of action common to several antidepressant 
treatments. To avoid the misleading results 
that can be obtained from small sample sizes, 
we have now scanned a total of 44 
unmedicated, moderately depressed patients 
with MDD and 35 age- and gender-matched 
healthy controls, which is about twice the 
size of most PET studies in psychiatry. 
Notably, about half the patients were 
treatment-naïve. 11C-(R)-rolipram binding in 
the brain was measured using arterial 11C-
(R)-rolipram levels to correct for the 
influence of cerebral blood flow. MDD 
subjects showed a widespread, 18% reduction in 11C-(R)-rolipram binding (p=0.001) that was not 
caused by different gray matter volumes (Fig 3). Decreased rolipram binding of similar 
magnitude was observed in most brain areas. Rolipram binding did not correlate with the 
severity of depressive or anxiety symptoms. These results were the first to demonstrate that brain 
levels of PDE4, a critical enzyme that regulates cAMP, are decreased in unmedicated individuals 
with MDD in vivo. Furthermore, the results are in line with human postmortem and rodent 
studies demonstrating downregulation of the cAMP cascade in MDD, and support the hypothesis 
that PDE4 inhibitors—which increase cAMP cascade activity—may have antidepressant effects.  
The Effect of Chronic Antidepressants on PDE4 Binding Building on this work, we 
sought to determine if antidepressant treatment upregulates PDE4 in humans as it does in 
animals. In addition to the rolipram PET scans without medication reported above, 23 of the 44 
unmedicated MDD patients had a follow up rolipram scan after starting treatment with SSRIs. 
Preliminary analyses show that these patients had a 12 ± 36% increase in rolipram binding after 
SSRI treatment across all brain regions (p < 0.001 when age was used as a covariate). The 
change in rolipram binding after SSRI varied markedly among patients, as indicated by the large 
standard deviation of 36%. In contrast, 13 healthy controls who had a repeat scan without SSRI 
showed similar binding on repeat scans with changes of only -1 ± 13%. Age affected the 
magnitude of SSRI-induced increase in rolipram binding; older patients showed greater increases 
after SSRI (p ≤ 0.001). However, no correlation was observed between rolipram binding and 
symptom severity, neither for the unmedicated baseline scan nor in response to SSRI treatment, 
possibly because of the heterogeneity of the disorder or the heterogeneity of PDE4, which has 
four distinct subtypes. 
Fig 3.  11C-(R)-rolipram binding was globally decreased 
by 18% in brains of unmedicated MDD patients during 
a major depressive episode (n = 44) compared to 
matched controls (n = 35; p = 0.001). These mean 
parametric images of the two groups represent the 
“absolute” quantitation of radioligand binding 
calculated on an individual voxel level and using the 
concentration of radioligand in serial arterial blood 
samples.  


 
 
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Taken together, these results elucidate two important and related points. First, the cAMP 
cascade, as indirectly measured with PDE4 binding, was downregulated in unmedicated patients 
with MDD. Second, antidepressant treatment normalized this downregulation. These studies 
suggest that PDE4 inhibition, perhaps via subtype selective agents, might again be assessed for 
efficacy in MDD; the results also broadly support the cAMP theory of depression and of 
antidepressant action. Additionally, cognitive benefits may be elicited over a broad range of 
disorders including Alzheimer’s disease, schizophrenia, and Parkinson’s disease. 
 
Development of a novel PET ligand to selectively image PDE4D 
 
MIB/NIMH and Tetra Discovery Partners developed several PDE4D selective PET 
ligands and tested them in monkey PET scans. Among these candidates, 11C-T-1650 showed the 
best results. Because PDE4 type B and type D have similar structures, type D selective ligands 
were developed based on 3D structural differences between type D and B [3]. Based on in vitro 
experiments using recombinant DNAs of human PDE4B and D, T-1650 has 300 times greater 
affinity to PDE4D than to PDE4B. Monkey PET scans showed moderate brain uptake peaking at 
3 SUV and was washed out to 1/3 of the peak in two hours, which allowed precise quantification 
of ligand binding, including both association to and dissociation from PDE4D (Figs. 4 and 5). 
Both VT (total uptake) and BPND (ratio of specific to nonspecific uptake) of 11C-T-1650 were 
greater than that of 11C-(R)-rolipram, even though T-1650 binds to only PDE4D, while rolipram 
binds to all PDE4 subtypes (Table 1). As described above, 11C-(R)-rolipram has been 
successfully used in rodent, healthy humans, and patients. Therefore, 11C-T-1650 is expected to 
be useful to study PDE4D in human. 
0
30
60
90
120
0
1
2
3
4
Time (min)
Brain activity (SUV)
 
Fig. 4. Specific binding of 11C-T1650 was blocked with  
Fig. 5. 11C-T-1650 showed good brain uptake 
rolipram (1 mg/kg). 
 
 
 
 
and clear washout in all brain areas. 
 
 
As background, we previously studied a radioligand for another subtype of PDE4 (i.e., 
PDE4B) in protocol 17-M-0041, which was terminated. The primary outcome measures were 
identifiability and time stability of distribution volume (VT). This radioligand for PDE4B had 


 
 
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significant flaws in healthy human subjects, based on studies here and at the Karolinska 
Institutet. Specifically, time stability of VT was consistent with radiometabolites accumulating in 
the brain. In addition, Pfizer will not allow us to use their therapeutic candidate, which also has 
major limitations (low bioavailability and short half-life). For these two reasons, we terminated 
the protocol using the PDE4B radioligand. 
 


 
 
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Table 1. Total distribution volume (VT) and specific-to-nondisplaceable ratio (BPND) of 11C-
T-1650 and 11C-(R)-rolipram in monkey 
 
VT 
BPND 
 
T-1650 
(R)-Rolipram 
T-1650 
(R)-Rolipram 
Prefrontal cortex 
10.8 
4.9 
1.6 
0.6 
Temporal cortex 
9.7 
5.1 
1.3 
0.7 
Putamen 
6.7 
5.5 
0.6 
0.8 
VND measured by Lassen occupancy plot by blocking with rolipram (1 mg/kg): 
11C-T-1650: 4.2; 11C-(R)-rolipram: 3.0 
 
Development of PDE4D inhibitor BPN14770 and initial tests in animals 
BPN14770 is a first-in-class, subtype selective, phosphodiesterase type-4D-negative 
allosteric modulator (PDE4D-NAM)[14]. The unique mechanism of action and subtype 
selectivity distinguishes BPN14770 from the two approved PDE4 inhibitors, roflumilast 
(Daliresp™) and apremilast (Otezla™). Roflumilast and apremilast are competitive inhibitors 
that inhibit the PDE4 enzymes by binding in the active site competitively with cAMP. As the 
amino acid sequence of the PDE4 active site is conserved between the four subtypes, roflumilast 
and apremilast inhibit all subtypes of PDE4 equally strongly. Both compounds cause emesis in 
humans and other species, and as a class, PDE4 competitive inhibitors have been found to cause 
mesenteric vasculopathy in rats, dogs and primates, although this toxicity has not been observed 
in humans. In contrast, BPN14770 does not cause emesis in ferrets, cynomolgous monkeys or 
marmosets and does not cause mesenteric vasculopathy in rats or dogs in toxicological studies of 
28 days duration. Thus, BPN14770 presents a unique procognitive and preclinical safety profile. 
Clearance of BPN14770 by hepatocytes from human, rat, dog and monkey, expressed as 
hepatic extraction ratio (EH), was 16%, 8.2%, 17%, and 12%, respectively. Qualitative 
metabolite profiling in human, rat, dog, and monkey hepatocytes showed a single metabolite in 
human (<1% parent). BPN14770 was highly bound to plasma proteins in all species tested. The 
fraction unbound (free) was 0.5, 0.4, 0.2, and 0.5%, for mouse, rat, dog, and human, respectively.  
BPN14770 is highly bioavailable in rats, mice and dogs (F% = 100), distributes to the 
brain (B/P = 0.32-0.48), and has a plasma t½ of 4.8 hours in rats, 10.9 hours in mice, and 11 
hours in dogs. The multi-species pharmacokinetic data suggest that BPN14770 will have 
adequate half-life for once daily oral administration in humans. In bile duct cannulated rats, 
BPN14770 was found to be eliminated as a conjugate through the bile. Only the unchanged drug 
was detected in plasma, and no BPN14770 was detected in urine. 
BPN14770 has cognitive benefit in the mouse Novel Object Recognition (NOR) test at 
0.3 mg/kg PO and above as shown by an increase in the Discrimination Index. BPN14770 Cmax 
at the minimum effective dose (MED) was 160 ng/mL in plasma and 40 ng/g in the brain. 
Cognitive benefit is maintained after chronic dosing for 7 days. BPN14770 also has benefit in a 
mouse model of cholinergic impairment, the scopolamine-impaired Y-maze (male C57Bl6 mice 
MED = 1 mg/kg). 
BPN14770 did not affect cardiovascular function in beagle dogs at doses up to 100 
mg/kg, nor did the compound affect respiratory function or exert neuropharmacologic effects in 
rats at doses up to 60 mg/kg. In the in vitro hERG assay, an increase in current of 12% and 33% 
was seen at concentrations of 10 and 30 μM, respectively. No IC50 could be calculated due to this 
increase in current. 


 
 
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In a rat 28 day toxicology study BPN14770 was well tolerated up to 60 mg/kg with no 
deaths on study, and no hematology, clinical chemistry, liver weight or gross necropsy findings. 
There were no microscopic findings. Unlike competitive PDE4 inhibitors such as roflumilast 
(Daxas™) and apremilast (Otezla™), BPN14770 did not cause mesenteric vasculopathy at the 
doses studied. 
In a dog 28 day toxicology study, the no observed adverse effect level (NOAEL) for 
BPN14770 was 30 mg/kg. At 100 mg/kg BPN14770 caused inappetence and weight loss and in 
female dogs an approximately 30 msec increase in QTc with a concomitant increase in heart rate 
of 10 bpm. Based on the lack of inhibition of hERG and the associated gastrointestinal 
disturbance, this change likely reflects an indirect effect on QTc. There were no changes in 
hematology and ophthalmology. Macroscopic observations included pale livers in two of eight 
animals at 100 mg/kg which correlated with mild alanine transaminase (ALT) elevation only in 
those two animals. Microscopic changes of peri-portal hepatocellular cytoplasmic vacuolation 
were observed in the livers of one male and two female dogs at 100 mg/kg. No liver changes 
were observed in recovery dogs suggesting that these changes, if present, were reversible. 
 
Clinical trials of BPN14770 in healthy subjects 
 
Tetra Discovery has completed the following two trials of BPN14770 in healthy subjects. 
 
BPN14770-CNS-101: a randomized, double-blind, placebo controlled, ascending single dose study 
to evaluate the safety, tolerability, and pharmacokinetic profile of BPN14770. in healthy subjects (18 
– 55 years old). 
 
BPN14770-CNS-102: a randomized, double-blind, placebo-controlled, multiple ascending dose 
study to evaluate the safety, tolerability, and pharmacokinetic profile of BPN14770 in healthy young 
(25 – 44 years old) and elderly (60 – 78 years old) male and female subjects, and to provide a 
preliminary assessment of the cognitive effects of BPN14770 in healthy elderly subjects. Each 
subject was randomized to receive a fixed daily dose of either BPN14770 or placebo twice daily 
(every 12 hours, or BID) or once daily (every 24 hours, or QD) for 8 consecutive days 
 
The following is the summaries of the results of these studies reported in the Investigator’s 
Brochure. 
 
BPN14770-CNS-101: 
 
Twenty-four subjects received BPN14770 (six at each dose level: 5mg/15mg/50mg/100mg) 
and eight subjects received placebo. Detectable plasma BPN14770 concentrations were measured 
after dosing starting between 0.5 hour and 1 hour after dosing, continuing through 48 hours after 
dosing for all four dose levels. Drug absorption was variable but moderately rapid with median Tmax 
values ranging from 1.5 to 3 hours. The plasma pharmacokinetics of BPN14770 after oral 
administration appeared to be linear for single doses ranging from 5 to 100mg, although a slight trend 
for a greater than proportional increase in exposure was observed in the 100mg group as compared to 
the lower dose groups. The apparent terminal elimination half-life of BPN14770 was consistent 
among dose groups and averaged between 11 and 13 hours. 
 
The following adverse events were reported. 


 
 
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Table 2. Adverse events after one oral dose of BPN14770 
AEs that occurred in more than one subject that were considered related to treatment consisted of 
nausea (reported by 4 of 6 subjects in the 100mg dose group), vomiting (reported by 2 of 6 subjects 
in the 100mg dose group, both of which also reported nausea) and diarrhea (reported by 2 of 8 
subjects in the placebo group and 1 subject each in the 5mg and 50mg BPN14770 dose groups). All 
but one treatment-emergent AE were mild or moderate in severity. One severe AE was reported for 
one subject in the 15mg dose group, who reported intermittent severe renal colic starting 
approximately 24 hours after dosing. 
 


 
 
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BPN14770-CNS-102: 
Table 3. Overview of study cohorts for 8-day oral administration of BPN14770 
 
 
The following results were obtained: 
1. Multiple doses of BPN14770, were administered twice daily (15 mg, 30 mg, or 50 mg) or once 
daily (75 mg) to healthy young subjects and twice daily (10 mg, 20 mg, or 40 mg) to healthy elderly 
subjects.  
2. There was evidence of greater than proportional increases in BPN14770 exposure after a single 
dose or repeated dosing. Drug accumulation was approximately 2-fold after QD dosing. After BID 
dosing, moderate drug accumulation (approximately 3- to 5-fold) was observed. Steady state 
appeared to be reached within 2 to 4 days of BID or QD dosing. When adjusted for differences in 
dose, mean BPN14770 exposure appeared to be similar between healthy young and healthy elderly 
subjects.  
 
The following adverse events were reported: 


 
 
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Table 4. Adverse events in 8-day oral administration of BPN14770 
No deaths or other serious adverse events were reported across the young and elderly cohorts, 
and no subject withdrew from the study due to adverse events. The majority of AEs were of mild 
severity. Two moderate AEs (nausea and vomiting) were reported by 1 subject in the 75-mg QD dose 
group; no other AEs of moderate severity were reported across the young cohorts.  
Of the 27 adverse events reported by young subjects who received active drug, a total of 20 
AEs observed in 9 subjects were considered by the Investigator as related to study treatment.  
No clinically significant effects of multiple oral doses of BPN14770 administered twice daily (15 
mg, 30 mg, or 50 mg) or once daily (75 mg) to healthy young subjects and twice daily (10 mg, 20 
mg, or 40 mg) to healthy elderly subjects were observed on biochemistry, hematology, or urinalysis; 
vital signs; or ECGs.  
Overall, no deaths or serious adverse events were reported during the study. No subjects 
withdrew from the study due to adverse events, and all treatment-emergent adverse events resolved 
without sequelae by the follow-up visit. One subject withdrew consent for treatment, which the 
Investigator determined was not a withdrawal for an AE, although she had a headache which had not 
fully resolved.  
Adverse events that occurred in more than 1 subject within a dose group or placebo group 
that were considered related to study drug were limited to the 40-mg BID dose group. Headache was 
reported in 4 of 10 subjects; diarrhea, increased alanine aminotransferase and aspartate 
aminotransferase, and hot flush were each reported in 2 of 10 subjects.  
The majority of AEs were of mild severity. A total of 3 moderate AEs were reported across 
the elderly cohorts; 2 moderate AEs (hypotension, dizziness) were reported by 1 subject in the 10-mg 
BID dose group, and 1 moderate AE (headache) was reported by 1 subject in the 40-mg BID dose 
group. 
 


 
 
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The rationale for selecting the dose of BPN14770 in this PET protocol 
 
We will administer 50 mg BID of BPN14770 for the following reasons. In a multiple dose 
study in healthy volunteers, a dose of 50 mg bid for 8 days was very well tolerated in young  
individuals (25 to 44 years old).  Only 2 of 6 reported any AE: one mild diarrhea and one mild 
nausea.  Both AEs were transient and neither led to discontinuation.  In elderly individuals (age 
>60) BPN14770 40 mg was also well tolerated over 8 days, with no discontinuations for adverse 
events.  The most common AE was transient headache in 4 of 10 individuals; 2 of 10 reported 
diarrhea compared to 1 on placebo.   
 
2. Study Objectives  
a. Primary objectives 
 
This study has three primary objectives. First, we will determine whether the uptake of 
11C-T-1650 in the brain reflects the distribution of PDE4D, as demonstrated by blocking with a 
PDE4D selective medication BPN14770. Second, we will measure binding site occupancy of 
BPN14770 and compare these data to plasma levels of the drug. Third, we will measure the 
test/retest reproducibility of brain uptake quantified by kinetic modeling and using arterial blood 
samples. 
b. Secondary objectives 
The secondary objective is to estimate dosimetry (i.e., radiation-absorbed doses) of 11C-T-1650. 
 
3. Subjects 
a.  Description of study populations  
We propose to study four groups of participants: 
Phase 1: One subject will have a whole body PET scan with 10 mCi of 11C-T-1650 to 
confirm that no organ has prominently high uptake of 11C-T-1650. 
 
Phase 2: 15 healthy subjects will have three brain PET scans, baseline, about 90-180 min 
after the first dose of BPN14770 (Scan #2), and after three and a half-day administration 
of BPN14770 (Scan #3) to measure specific binding and BPND of 11C-T-1650 and binding 
site occupancy of BPN14770. The dose of BPN14770 is 50 mg BID (except for the last 
day in which subjects will take a single dose).  BPN14770 levels will be measured in 
plasma samples. 
 
Phase 3: Nine healthy subjects will have a whole body scan using 20 mCi 11C-T-1650 to 
estimate radiation-absorbed doses. 
 
Phase 4: 15 healthy subjects will have two brain PET scans; test-retest kinetic brain 
imaging with arterial blood sampling. 
 
Note: As described below in Section 10 (“Statistical Analysis”), these requested numbers 
account for and include subjects who may drop out. 
 
b.  Inclusion criteria 
All phases 
1. Age ≥ 18. 
2. Able to give written informed consent. 
3. Medically and psychiatrically healthy. 


 
 
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4. Enrolled in 01-M-0254 “The Evaluation of Participants with Mood and Anxiety Disorders 
and Healthy Volunteers” (PI: Dr. Carlos Zarate) or 17-M-0181 “Recruitment and 
Characterization of Healthy Research Volunteers for NIMH Intramural Studies” (PI: Dr. 
Joyce Chung). 
 
Additional inclusion criterial for Phase 2 
1. Age ≤ 55. 
2. Body mass index between 18 kg/m2 to 32 kg/m2, inclusive, and body weight of ≥50 kg 
(110 pounds). 
3. Female subjects must be surgically sterile (bilateral tubal ligation, hysterectomy, or 
bilateral oophorectomy at least 6 months prior to dosing of BPN14770), at least two years 
post-menopausal, or willing to use two barrier methods of contraception from initial 
screening until one month after taking the last dose of study drug.  
4. Male subjects must be willing to inform female partners of their participation in the study 
and must agree to use adequate contraceptive methods (vasectomy performed at least 6 
months prior to dosing BPN14770 or use at least one barrier method of birth control). 
 
c.  Exclusion criteria –All phases 
All phases 
1. Clinically significant laboratory abnormalities based on the following tests (performed 
under screening protocol 01-M-0254 or 17-M-0181): CBC; acute care panel; hepatic 
panel; mineral panel; urinalysis; urine drug screen; urine pregnancy test (females); and 
lipid panel; hepatitis panel (A, B, C); syphilis screening test; total protein; uric acid; 
creatine kinase; cholesterol; thyroid panel; prothrombin and partial prothrombin tests; and 
EKG. 
2. Have a brain disease (such as multiple sclerosis or stroke).  
3. Any current Axis I diagnosis, based on interview and self-reporting performed under 
screening protocol 01-M-0254 or 17-M-0181. 
4. Positive HIV test. 
5. Current or past history of significant cardiovascular, cerebrovascular, pulmonary, renal, 
or liver disease. Stable, well-controlled hypertension and hyperlipidemias are allowed. 
6. Taking psychotropic drugs (i.e. benzodiazepines or antidepressants) including sedative 
antihistamines; moderate to strong inhibitors or inducers (i.e. fluconazole or 
ciprofloxacin) of any CYP450 enzyme. A complete listing of such inhibitors or inducers 
may be found in Attachment 1, List of P450 inhibitors.  
7. Recent exposure to radiation related to research (e.g., PET from other research) that, 
when combined with this study, would be above the allowable limits. 
8. Inability to lie flat on camera bed for at least two hours. 
9. Pregnancy or breastfeeding.  
10. Positive screen for drugs of abuse or cotinine (at screen or upon admission), or a positive 
alcohol result (upon admission). 
11. Current use of psychiatric medications. 
12. NIMH employees and staff or immediate family members of NIMH employee/staff. 
 
Additional exclusion criterial for Phase 2 and 4 
1. coagulation disorder;  


 
 
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2. thrombocytopenia;  
3. Found to have inadequate collateral circulation of the radial artery (see section 5.c 
screening below) 
4. Are unable to have an MRI scan (e.g., pacemakers or other implanted electrical devices, 
brain stimulators, dental implants, aneurysm clips (metal clips on the wall of a large 
artery), metallic prostheses (including metal pins and rods, heart valves, and cochlear 
implants), permanent eyeliner, implanted delivery pumps, or shrapnel fragments, metal 
fragments in the eye) 
 
Additional exclusion criterial for Phase 2 
1. Marked bradycardia (heart rate ˂45 beats per minute [bpm]) or tachycardia (heart rate 
˃110 bpm) based on supine ECG values obtained at Screening, before the first dose of 
BPN14770 on the day of the study. Out-of-range vital signs may be repeated once at each 
eligibility assessment (prior to the start of dosing). 
2. History of hematological disorders (e.g., thrombocytopenia) in the immediate family (i.e., 
parents and siblings). 
3. Clinically important or significant conduction abnormalities on single ECG (including 
QTc interval ˃450 msec) or evidence or history of long QT syndrome. This exclusion 
applies to the ECGs obtained at Screening, before the first dose of BPN14770 on the day 
of the study. 
4. Current or past history of gastric or duodenal ulcers or other diseases of the 
gastrointestinal tract that could interfere with absorption of study drug. Note: Subjects 
with a history of appendectomy or cholecystectomy may be enrolled. 
5. Active acute or chronic infectious diseases. 
6. Any history of alcohol or drug abuse within the previous year prior to the Screening visit 
(per the current edition of the Diagnostic and Statistical Manual of Mental Disorders, 5th 
Edition: DSM-5), or regular (daily) consumption of alcohol exceeding two bottles of 
beer, or the equivalent amount of other forms of alcohol (1 serving = 12 oz beer, 5.0 oz 
wine, or 1.5 oz distilled spirits). 
7. Unwilling to abstain from alcohol within 72 hours of before the first dose of BPN14770. 
8. Currently ingest nicotine in any way (including smoking cigarettes, vaping, and via 
patch), or have ingested any nicotine products within the past 3 months.  
9. Participation in other clinical studies involving investigational drug within the previous 
30 days prior to the first day of the study. 
10. Unwilling to forgo donation of blood or blood products (including plasma) during the 8 
weeks before the first day of the study. 
11. History of allergy to penicillin or sulfonamides, or any other clinically significant drug 
allergy that includes symptoms such as shortness of breath, rash, or edema. 
12. A suicidal ideation intensity score of 2 or higher per screening C-SSRS assessment 
and/or any suicidal behavior within the past 30 days. 
 
 
 
4. Study Design and Methods 
a. Study overview 


 
 
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This is a single center study in healthy volunteers. Healthy volunteers will be screened 
under protocol 01-M-0254 or 17-M-0181. As noted above, participants must meet inclusion and 
exclusion criteria and sign an informed consent document. The four phases of this study will be:  
 
1) initial first-in-human whole-body imaging of one subject with a low injection activity 
of 10 mCi;  
 
2) brain imaging at baseline (Scan #1), about 90-180 min after the first dose of 
BPN14770 (Scan #2), and after three and a half-day administration of BPN14770 (Scan #3) to 
measure specific binding and BPND of 11C-T-1650 and binding site occupancy of BPN14770.  
Binding site occupancy in the brain will be compared to plasma levels of BPN14770.  The 
measurement of BPND by Lassen occupancy plot [15] assumes no change in PDE4D density after 
administering BPN14770. Comparison between Scan #1 (baseline) and Scan #2 (90-180 min 
after the first dose of BPN14770) allows the measurement of BPND with little changes in PDE4D 
density. Comparison between Scan #1 and Scan #3 allows measurement of binding site 
occupancy by BPN14770 at a steady state level.  
 
3) whole body imaging to estimate radiation-absorbed doses of 11C-T-1650, and  
 
4) test-retest kinetic brain imaging with arterial blood sampling.  
 
In the past, the NIH Radiation Safety Committee (RSC) required that whole body 
imaging be performed first in several subjects for any new radioligand to estimate radiation 
exposure to the body. However, if the radioligand subsequently proved ineffective for brain 
imaging, then these subjects who underwent whole body imaging would have been unnecessarily 
exposed to radiation. For this reason, the RSC allowed brain imaging using new 11C- and 11F-
labeled radioligands to be performed after doing whole body imaging in one subject in order to 
determine whether the radioligand was worth pursuing as a brain imaging agent. That is, ‘go / 
no-go’ decisions are made on a small number of subjects based on brain imaging. The request to 
do so in this protocol follows the identical steps approved for another protocol (14-M-0068, 
“Evaluation of a Novel Positron Emission Tomography (PET) Radiotracer for TARP γ-8”). 
 
We propose to study up to 40 healthy volunteers: one in Phase 1 (whole body imaging 
with a low injection activity), 15 in Phase 2 (baseline and blocked brain scans), 9 (whole body 
imaging to estimate radiation-absorbed doses, and 15 in Phase 4 (test-retest kinetic brain imaging 
with arterial blood sampling).  
To estimate the radiation exposure from this new radioligand, we will follow the prior 
suggestions from our laboratory [16], which have been approved by the NIH RSC. Specifically, 
we found that the average exposure of all published human studies with 11C-radioligands more 
accurately reflected the exposure to humans than estimation based on imaging in monkeys with 
that particular radioligand. 
 
Phase 1: One subject will have a first-in-human whole body PET scan with 10 mCi 11C-
T-1650 to confirm that no organ has prominently high uptake of 11C-T-1650. 
 


 
 
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Phase 2: 15 healthy subjects will have three brain PET scans, baseline (Scan #1), about 
90-180 min after the first dose of BPN14770 (Scan #2), and after three and a half-day 
administration of BPN14770 (Scan #3). In each scan, 20 mCi of 11C-T-1650 will be 
injected. In Scan #1 and #2, the binding will be measured by kinetic brain imaging with 
arterial blood sampling. In addition, in all of Scan #1, 2, and 3, by using venous samples, 
radioligand binding will be measured as brain uptake (SUV) normalized to venous 
concentrations of 11C-T-1650 because an arterial line will not be placed in Scan #3 due to 
three-day interval between Scan #2 and 3.  Venous samples will be analyzed for 
BPN14770 levels.  The dose of BPN14770 will be 50 mg BID (except for the last day in 
which subjects will take a single dose). 
 
Phase 3: Nine healthy subjects will have a whole-body scan using 20 mCi of 11C-T-1650 
to estimate radiation-absorbed doses. 
 
Phase 4: 15 healthy subjects will have two brain PET scans; test-retest kinetic brain 
imaging with arterial blood sampling. 
 
 
If Phase 2 shows substantial specific (i.e., displaceable) binding, we will be confident that 
the radioligand itself can be used to measure the density of PDE4D in human subjects, including 
patients with MDD. For such potential studies, we will need to determine dosimetry and test / 
retest variability of the PET scans, independent of the results from three-day administration of 
BPN14770. Thus, if Phase 2 shows substantial (>40%) specific binding in three subjects, we will 
simultaneously proceed with Phases 2, 3, and 4. 
Brain MRI and PET scans are part of the protocol. There will be no brain MRI in the 
whole body dosimetry studies in Phases 1 and 3. The MRI will be obtained within 12 months of 
the PET scans (i.e., up to 12 months before or after the PET scan) and can be performed on the 
same day. Brain PET scans will be performed with vital sign monitoring. In Phase 2 and 4, 11C-
T-1650 brain PET scans will be associated with arterial sampling for the input function 
measurement except Scan #3 in Phase 2. No arterial input function will be taken for the Phases 1 
or 3 studies, however, several venous samples may be obtained in these studies to guide the 
analysis of arterial samples obtained in the brain scans.  
 
Number of visits and time commitment of participants. 
The visits are described below and summarized in Table 5. 
Phase 1: whole body imaging with 10 mCi injection 
1st outpatient visit: pregnancy test; whole body PET (4 hours) 
 
Phase 2: brain imaging (20 mCi) at baseline and after BPN14770 
1st outpatient visit: pregnancy test; MRI (2 hours) 
2nd outpatient visit: pregnancy test; baseline brain PET imaging (4 hours) 
3rd outpatient visit: pregnancy test, brain PET imaging starting approximately 90-180 min after 
the first dose of PDE4D selective inhibitor BPN14770 (6 hours). BPN14770 (50 mg BID) 
administration will be continued for three and a half days (the last day subjects will take a 
single dose). 
4th outpatient visit: On the last day of BPN administration. The third PET scan will be started 
about 90-180 min after the last dose of BPB14770 (4 hours) 


 
 
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5th outpatient visit: 3 -7 days after the last dose of BPN14770 
 
The first two brain PET scans may be performed on a single or two different days, based 
on the availability of the subject and the PET camera. The order of the visits for MRI and PET 
scans may be changed based on the availability of the scanners. The baseline PET scan and the 
first PET scan after BPN14770 administration may occur on the same day and, if so, be 
separated by at least 2.5 hours to allow for decay of the first injection (T1/2 = 20 min). 
 
Phase 3: whole body imaging with 10 mCi injection 
1st outpatient visit: pregnancy test; whole body PET (4 hours) 
 
Phase 4: test retest kinetic brain imaging (20 mCi) 
1st outpatient visit: pregnancy test; MRI (2 hours) 
2nd outpatient visit: pregnancy test; brain PET (4 hours) 
3rd outpatient visit: pregnancy test; retest brain PET (4 hours) 
The PET scans may be performed on one day or on two different days. The order of the 
visits for MRI and PET scans may be changed based on the availability of the scanners. Both 
PET scans may occur on the same day and, if so, be separated by at least 2.5 hours to allow for 
decay of the first injection (T1/2 = 20 min). 
 
Table 5. Number of visits and time commitment of participants 
Visit #1 
Visit #2 
Visit #3 
Visit #4  
Visit #5 
Phase 1 
Pregnancy test; 
Whole-body PET scan  
(4 hours) 
N/A 
N/A 
N/A 
N/A 
Phase2 
Pregnancy test; Brain 
MRI  
(2 hours) 
Pregnancy test; 
Brain PET scan #1 
(4 hours) 
Pregnancy test; 
BPN14770 admin.; 
Brain PET scan #2  
(6 hours) 
Pregnancy test;  
Brain PET scan #3  
(4 hours)  
Examination 3-7 
days post last dose 
of BPN14770 
Phase 3 
Pregnancy test; 
Whole-body PET scan  
(4 hours) 
N/A 
N/A 
N/A 
N/A 
Phase 4 
Pregnancy test; Brain 
MRI  
(2 hours) 
Pregnancy test; 
Brain PET scan #1 
(4 hours) 
Pregnancy test;  
Brain PET scan #2  
(4 hours) 
N/A 
N/A 
* The MRI may be scheduled on the same day as a PET scan 
** MRI does not need to be performed if participant has had an adequate MRI within 12 months 
of the brain PET scan. 
 
b. Recruitment 
Healthy volunteers will be recruited under 01-M-0254 or 17-M-0181 and not under the 
current protocol. NIH Employees/staff will not be directly recruited by or through their 
supervisors or co-workers to participate in this study. 
 
c. Screening 
 
Healthy volunteers will be screened under protocol 01-M-0254, “The Evaluation of 
Participants with Mood and Anxiety Disorders and Healthy Volunteers” (PI: Dr. Carlos Zarate) 


 
 
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or 17-M-0181 “Recruitment and Characterization of Healthy Research Volunteers for NIMH 
Intramural Studies” (PI: Dr. Joyce Chung). Basic screening will include physical exam, medical 
and psychiatric history, and laboratory tests: CBC; acute care panel; hepatic panel; mineral 
panel; urinalysis; urine drug screen; urine pregnancy test (females); and lipid panel; hepatitis 
panel (A, B, C); syphilis screening test; total protein; uric acid; creatine kinase; cholesterol; 
thyroid panel; prothrombin and partial prothrombin tests; and EKG. The radial artery pulse is 
checked for the presence of adequate ulnar collateral flow and the absence of any metals or 
foreign objects in bilateral wrists. Screening results will be reviewed by a clinically credentialed 
investigator before the subject undergoes any specific study procedures. 
 
d. Study procedures 
Consent will be obtained before any study procedures are done. Subjects participating in 
Phase 2 and 4 will receive three (Phase 2) or two (Phase 4) 11C-T-1650 brain PET scans and a 
brain MRI scan. During the PET scan, arterial blood samples will be drawn. The MRI scan may 
be obtained before, after, or between the two PET scans. The MRI will be performed with a 3 
Tesla magnet at the NIH. 
Subjects participating in Phases 1 and 3 will receive one 11C-T-1650 whole body PET 
scan. No MRI will take place in these dosimetry/enzyme occupancy studies. All procedures are 
solely for research purposes. 
 
MRI 
 
For participants to Phase 2 and 4, A brain MRI will be obtained for anatomic localization 
and will be performed on a 3 Tesla scanner located at the NIH Clinical Center and will take 
about one hour. Participants who have had an adequate brain MRI performed at the NIH within 
12 months of the dedicated brain PET scan will be exempt from this part of the protocol and their 
earlier MRI will be used for anatomical localization. Pregnancy tests: For women able to become 
pregnant, urine pregnancy testing will be done within the 24 hours prior to any MRI or PET 
scan.  PET and MRI will not be done if the pregnancy test is positive. 
 
 
PET Procedures 
1) Radioligand 
11C-T-1650 will be prepared according to the IND and administered via an indwelling 
intravenous catheter over approximately one minute. 
 
2) PET Brain Imaging 
After midnight on the day before, participants are not allowed to take caffeine containing 
drink because caffeine is a nonselective inhibitor of phosphodiesterases. Dedicated brain imaging 
will be performed using a PET or PET/CT scanner for two to three hours. Participants will be 
placed on the scanner bed with their head held firmly in place with a thermoplastic mask fixed to 
the bed. A 68Ge, 137Cs, or CT transmission scan will be performed to measure and correct for 
attenuation. Tracer infusions will be performed when the subject is already on the scanner bed. 
After an intravenous bolus of up to 20 mCi, arterial blood samples will be drawn from the 
arterial catheter during the PET scan. We will collect about 10-20 arterial samples. The sampling 
will be performed either at discrete time points and/or continuously. In Phase 2, before and after 
administration of BPN14770, a few samples (< 7) will be obtained to measure concentration of 


 
 
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BPN14770 during each of second and third PET scans. In addition, during each scan of Phase 2, 
a few venous samples (< 7) will also be obtained to compare venous data of Scan 3 with those in 
Scan 1 and 2 because it is difficult to place an arterial line with an interval of three days between 
Scan 2 and 3. Brain uptake (SUV) normalized to venous blood data will be used to compare scan 
1 and 3. 
The total amount of sampling volume will be about 150 mL in each brain scan. PET 
images will be acquired in three-dimensional mode with increased length of frame for a total of 
approximately two to three hours. If the scan lasts more than two hours, the subject will be 
offered a break out of the camera for approximately 15 minutes. Vital signs (blood pressure, 
pulse, and respiratory rate) and EKG (either 3- or 12-lead) will be recorded within three hours 
before tracer injection, and again about 15, 30, and 120 minutes after tracer injection. After the 
scan, the arterial and venous lines will be removed and the subject will be instructed to void 
frequently to minimize radiation exposure. 
 
3) PET Whole Body Imaging 
 
After midnight on the day before, participants are not allowed to take caffeine containing 
drink because caffeine is a nonselective inhibitor of phosphodiesterases. Whole body scans will 
be performed with a PET/CT scanner for about two hours. No arterial sampling will be done for 
dosimetry studies but a few venous samples (< 7) will be obtained to measure the concentration 
of the radioligand. Both a pre-injection transmission scan and a series of dynamic emission scans 
will be acquired. Each subject will be imaged in contiguous segments from the top of the head to 
a point below the gonads. To minimize extraneous motion, subjects will wear a head-holding 
mask and will have their arms and abdomen wrapped with body-restraining sheets. Almost all 
subjects find this restraint comforting (i.e., they are not afraid of falling off the table), and none 
have found it intolerable. Vital signs (blood pressure, pulse, and respiratory rate) and EKG 
(either 3- or 12-lead) will be recorded within three hours of tracer injection, and again about 15, 
30, and 120 minutes after tracer injection. 
 
Pregnancy tests:  For women able to become pregnant, urine pregnancy testing will be done 
within the 24 hours prior to any MRI or PET scan.  PET and MRI will not be done if the 
pregnancy test is positive. 
 
4) Arterial Line Placement 
After the presence of adequate ulnar collateral flow has been confirmed, a radial artery 
catheter will be inserted by the Anesthesiology Department or the Vascular Access Department. 
Before catheter insertion, the skin at the puncture site will be locally anesthetized. 
An arterial line will be placed in all brain scans except Scan 3 in Phase 2. Scan 3 in Phase 
2 will be performed without arterial line. Only venous samples will be obtained in Scan 3, and 
they will be used to compare Scan 3 with Scan 1 and 2.  
 
5) Preparation and administration of BPN14770 (Phase 2)  
BPN14770 will be provided by Tetra Discovery to NIH Clinical Center Pharmacy as 
capsules. Tetra Discovery will provide Quality Assurance to NIH Clinical Center Pharmacy. 
Participants will be encouraged to have a light meal prior to enzyme occupancy PET 
studies with blockade by BPN14770. Participants will be monitored by study clinicians after 
drug administration and during the PET scans to assess drug associated adverse events. On each 


 
 
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day while subjects take BPN14770 as an outpatient, a phone call will be made to participants 
who take part in Phase 2 to monitor any possible drug-associated adverse events. Contact 
information of a study clinician will be provided to participants in case they experience adverse 
reactions. 
If a technical problem causes a scan cancellation (e.g., radiochemistry production failure, 
PET camera malfunction, weather conditions, or unforeseen event in subject’s schedule) after the 
subject takes BPN14770 for three and a half days, subjects may continue to take BPN14770 for 
three more days (i.e., BPN14770 administration for six and a half consecutive days) and have 
Scan #3, if willing. 
 
6) Dietary Guidelines (Phase 2) 
• Subjects must not consume beverages or foods containing alcohol or grapefruit from 48 hours 
prior to the first dose of BPN14770 and within 48 hours after the last dose. 
• Morning doses will be taken after completing an overnight fast of at least 8 hours. Evening 
doses will be administered 12 hours after the morning dose and at least 1 hour after completing 
the evening meal. During the fasting periods, water will be allowed ad libitum. 
 
7) Lifestyle Guidelines (Phase 2) 
• Subjects are to refrain from physical activity greater than their normal level of activity from 48 
hours prior to the first dose of BPN14770 until the follow up visit 3 – 7 days after the last dose. 
 
8) Laboratory tests after BPN14770 administration (Phase 2) 
• On the day of the first dose of BPN14770, before the dose as well as after the PET scan, the 
following lab tests will be conducted: CBC; acute care panel; hepatic panel; mineral panel; 
urinalysis; lipid panel; total protein; uric acid; creatine kinase; cholesterol; thyroid panel. 
 
 
9) Follow up visit after BPN14770 (Phase 2)  
 
Adverse events (AEs), physical exams, vital signs, ECG readings, and clinical laboratory 
values will be assessed through the follow-up visit 3 -7 days after the last dose of BPN14770. 
Clinically significant AEs that occur during the study will be followed until resolution. 
 
e. End of participation 
Participants remain under the care of their own physicians during and after participation 
in this protocol. We will notify participants and, with their written permission, their doctors, of 
any clinically significant results from any procedure done under this protocol. 
 
5. Management of Data and Samples 
a. Storage 
We will follow NIH guidelines to prevent identification of study participants and other 
violations of subject confidentiality. Information will be stored using a confidential case number, 
and no identifiers (name, address, phone number, etc.) will be used that could allow direct 
linking of database information to individual subjects. Secure e-mail will be used for all 
electronic communications of subject information between investigators. Blood samples to 
measure 11C-T-1650 concentrations will be discarded at the end of the study. Blood samples to 


 
 
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measure BPN14770 will be kept in a locked freezer in MIB/NIMH in the NIH Bethesda campus. 
Demographic and clinical data will be archived on a password-protected server. 
All data will be stored on the NIMH server under password-protected accounts accessible 
only to the principal investigator and directly involved study personnel to preserve subject 
privacy. All data are regularly backed up, either by the NIMH system administrator or by NIMH 
CIT personnel. 
 
b.  Data and sample sharing plan 
No samples will be saved after completion of the study, and no samples will be shared. 
De-identified data will be shared with Tetra Discovery Partners, but the de-identified data will 
not be publicly available until publication of the results. However, de-identified data may be 
shared with collaborating laboratories at the NIH (e.g., Carlos Zarate) as part of planning for a 
potential clinical trial. When the data are made publicly available, they may be stored outside of 
the NIH and/or submitted to NIH-designated repositories and databases. Repositories receiving 
data from this protocol may be open-access or restricted access. 
Genomic data will not be obtained under this protocol. 
When data are shared, they will be stripped of identifiers and may be coded (“de-
identified”) or unlinked from an identifying code (“anonymized”). When coded data are shared, 
the key to the code will not be provided to collaborators, but will remain at the NIH. Data may 
be shared with investigators and institutions with an FWA or operating under the Declaration of 
Helsinki (DoH) and reported at the time of continuing review. Sharing with investigators without 
an FWA or not operating under the DoH will be submitted for prospective IRB approval. 
Submission to NIH-sponsored or supported databases and repositories will be reported at the 
time of the Continuing Review.  Submission to non-NIH sponsored or supported databases and 
repositories will be submitted for prospective IRB approval. 
Required approvals from the collaborating institution will be obtained and materials will 
be shipped in accordance with NIH and federal regulations.    
 
6. Additional Considerations 
a. Research with investigational drugs or devices 
This study involves two INDs, one for 11C-T-1650 and another for BPN14770. The IND for 
11C-T-1650 has not yet been submitted to the FDA. The IND for BPN14770, #127,905, is 
sponsored by Tetra Discovery Partners, Grand Rapids, MI. The drug will be stored according 
to the Investigator Brochure, which has been uploaded into PTMS. 
  
b. Gene therapy 
Not applicable. 
 
7. Risks and Discomforts 
a. Medical examination and laboratory testing 
 
Medical examinations, including phlebotomy for blood analysis, are associated with only 
minimal risk. There is usually some discomfort when the needle is inserted for phlebotomy. 
There is minimal medical risk associated with having an EKG. The patient may feel 
uncomfortable while the electrodes are attached to the chest. The conductive gel sometimes 
causes some mild irritation. 
 


 
 
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b. Radiation exposure risks 
 
Radiation exposure in this protocol will be from 11C-T-1650 and the associated 
transmission scans. To estimate the radiation exposure from this new radioligand, we will follow 
the suggestion from our laboratory [17] and approved by the NIH RSC and the FDA. 
Specifically, we found that the average exposure of all published human studies with 11C-
radioligands more accurately reflected radiation exposure than estimation based on imaging in 
monkeys with that particular radioligand. 
The average effective dose from 21 radioligands labeled with 11C was 0.019 rem/mCi 
[16]. Thus, the radiation exposure from a single injection of 20 mCi yields an effective dose of 
0.38 rem, not including the transmission scan (described below), which is well below the NIH 
limit of 5 rem. 
With regard to exposure from the transmission scan, the PET Department recently 
implemented Dr. Innis’s suggestion to decrease the current (amperage) and, thereby, the 
radiation from the CT. We do not need a high resolution (high current) image for attenuation 
correction; a low resolution, like that from a line source, is perfectly adequate to correct 
attenuation in the PET emission scan. With the lowered current, the exposure to the lens of the 
eye is now 0.26 rem, about 1/3 of the previous value. 
We wish to maintain flexibility in the choice of PET cameras. Among the various PET 
cameras, PET/CT has the highest exposure. The effective doses for one head and one whole 
body transmission scan from a PET/CT are 0.02 and 0.66 rem, respectively. In addition, we 
allow for up to two transmission scans in case the subject temporarily leaves the camera (e.g., to 
urinate) or moves significantly. 
 
The radiation exposure from the four phases of this protocol is as follows: 
Phase 1: Whole Body Scan. The effective dose comes from 10 mCi radioligand (= 0.38 / 
2 rem) plus two whole body transmission scans (2 * 0.56 rem) for a total of 1.31 rem. This dose 
is described in the consent form as “about 2 rem.” 
Phase 2: Three brain scans. The effective dose comes from three injections of 20 mCi 
radioligand (3 * 0.38 rem) plus up to six head transmission scans (6 * 0.02 rem) for a total of 
1.26 rem. This dose is described in the consent for as “about 1 rem.” 
Phase 3: One Whole Body Scan. The effective dose comes from one injection of 20 mCi 
radioligand (0.38 rem) plus up to two transmission scans (2 * 0.56 rem) for a total of 1.5 rem. 
This dose is also described in the consent form as “about 2 rem.” 
Phase 4: Two brain scans. The effective dose comes from two injections of 20 mCi 
radioligand (2 * 0.38 rem) plus up to four head transmission scans (4 * 0.02 rem) for a total of 
0.84 rem. This dose is described in the consent for as “about 1 rem.” 
 
Each subject will not participate in more than one phase of this study.  
 
 
c. PET scanning 
 
PET scans, which detect injected radioactivity within the body, are not associated with 
any known physical hazards to the subject lying on the table. We routinely use a series of 
procedures to minimize the risk of discomfort during scanning sessions. Namely, the procedures 
are conducted in the presence of trained health professionals to whom participants will have 
ready access should they experience any problems. Participants can communicate with the 


 
 
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trained health professionals while in the scanner and can be removed from the scanner and 
withdraw from the study at any time if they wish to do so. Participants can also request that the 
operator stop the scan. 
 
d. Arterial line placement 
Placement of a radial arterial catheter may cause bruising or infection. There is also a risk 
of occlusion and microemboli. Over 3,000 arterial catheters have been placed to date at NIH 
Clinical Center for PET scans. Of these, only two complications requiring physician’s care arose. 
In the first case, a small radial artery aneurysm developed several months later, which was 
successfully repaired surgically. In the second case, a radial artery thrombosis developed 28 days 
later, which was also successfully repaired surgically.  
 
e. Intravenous line placement 
Venous catheter insertion can be associated with discomfort, bruising, infection, or clot 
formation. Using proper placement techniques will minimize these risks. 
In case of tracer extravasation, we will stop the study, remove the venous line from the 
arm, and apply cold compress to the site. 
 
f. Blood sampling 
 
Participants will have arterial and venous blood sampling. The total amount of blood 
drawn will not exceed 500 mL. Some of the blood will be collected via phlebotomy and some 
through venous and arterial lines. Blood sampling may lead to the formation of small 
subcutaneous hematomas caused by blood leaking from a punctured blood vessel. Such 
hematomas cause only minor discomfort. They are not dangerous and require no treatment other 
than reassuring the patient. There is also a small risk of infection at the site of the needle 
puncture, which can be readily treated with antibiotic therapy We will ask participants not to 
donate blood within 8 weeks prior to the study or for 8 weeks following the study.   
 
g. MRI 
 
People are at risk for injury from the MRI magnet if they have pacemakers or other 
implanted electrical devices, brain stimulators, some types of dental implants, aneurysm clips 
(metal clips on the wall of a large artery), metallic prostheses (including metal pins and rods, 
heart valves, and cochlear implants), permanent eyeliner, implanted delivery pump, or shrapnel 
fragments. Welders and metal workers are also at risk for injury because of possible small metal 
fragments in the eye of which they may be unaware. Subjects will be screened for these 
conditions before having any scan, and if they have any, they will not receive an MRI scan.   
 
It is not known if MRI is completely safe for a developing fetus. Therefore, all women of 
childbearing potential will have a pregnancy test performed no more than 24 hours before each 
MRI scan. The scan will not be done if the pregnancy test is positive.  
People with fear of confined spaces may become anxious during an MRI. Those with 
back problems may have back pain or discomfort from lying in the scanner. The noise from the 
scanner is loud enough to damage hearing, especially in people who already have hearing loss. 
Everyone having a research MRI scan will be fitted with hearing protection. Subjects will be 
asked to complete an MRI screening form for each MRI scan they have. There are no known 
long-term risks associated with MRI scans. 
 


 
 
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h. BPN14770 administration  
 
Participants in Phase 2 will receive BPN14770 50 mg BID for three days, and a single 
dose of BPN14770 on the fourth day. Only minor adverse events are expected, which include: 
headache, diarrhea, nausea, vomiting, hot flashes, increased alanine aminotransferase and 
aspartate aminotransferase, hypotension, and dizziness.    
 
 
8. Subject Safety Monitoring 
Participants will be carefully monitored by clinical staff and asked about the presence of 
adverse events throughout the study, including during the PET procedure. The site of the catheter 
insertion will be carefully monitored for signs of bleeding. 
 
a. Parameters to be monitored 
For each 11C-T-1650 scan: Pulse rate, blood pressure, respiratory rate, and EKG (either 3- 
or 12-lead) will be recorded within three hours before tracer injection and again at about 15, 30, 
and 120 minutes after injection. Laboratory tests will be done before and after tracer 
administration to monitor for changes. Monitoring will be performed by a credentialed clinician. 
For BPN14770 (Phase 2): On the day of the first dose of BPN14770, before the dose as 
well as after the PET scan, the following lab tests will be conducted: CBC; acute care panel; 
hepatic panel; mineral panel; urinalysis; lipid panel; total protein; uric acid; creatine kinase; 
cholesterol; thyroid panel. 
In addition, 3 -7 days after the last dose of BPN14770, participants are asked to visit NIH 
to check the presence of adverse events. The following parameters will be monitored during the 
follow up visit: 
• Brief physical examination 
• Orthostatic (supine sitting, standing) blood pressure and pulse 
• ECG 
• Body weight. 
• CBC; acute care panel; hepatic panel; mineral panel; urinalysis; urine pregnancy test 
(females); and lipid panel; total protein; uric acid; creatine kinase; cholesterol; thyroid 
panel. 
 
b. Criteria for individual subject withdrawal 
Patients will be removed from the study if they become pregnant, are unable to continue 
to cooperate, or have an alteration in clinical status needing medical intervention. Patients may 
withdraw from the trial at any time at their own request. The investigators may withdraw a 
subject if the subject cannot meet study requirements, or the investigator deems that it is not in 
the subjects’ best interest to continue. 
 
9. Outcome Measures 
a. Primary outcome measures 
 
In baseline scans of 11C-T-1650, the primary outcome measure is its binding, specifically 
identifiability, stability over time, and retest variability of VT calculated with compartmental 
modeling. Phase 2 (BPN14770 administration) has two primary outcome measures, VND of 11C-
T-1650 and binding site occupancy of BPN14770. VND of 11C-T-1650 will be measured by 
comparing 11C-T-1650 binding (VT) between Scan #1 (baseline) and Scan #2 because arterial 


 
 
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data will be available to calculate VT. Binding site occupancy of BPN14770 under stable plasma 
concentrations of BPN14770 and VND of 11C-T-1650 will be measured by comparing Scan #1 
and #3 using brain uptake (SUV) normalized to venous concentrations of 11C-T-1650 because 
arterial line will not be placed for Scan #3 due to the short interval of the scans. 
 
b. Secondary outcome measures 
Biodistribution and dosimetry of 11C-T-1650. 
 
10.  Statistical Analysis 
a. Analysis of data/ study outcomes 
Brain imaging data will be analyzed with compartmental modeling using a nonlinear least 
squares analysis, graphical analysis of integration plot, and multilinear regression analysis. PET 
and MRI scans will be co-registered for anatomic definition of regions of interest. SUV will be 
calculated in various brain regions. Parametric images will be created using PMOD software 
(PMOD Technologies Ltd., Zurich, Switzerland 
 
b.  Power analysis 
This kinetic modeling will give us 11C-T-1650 binding values as well as their 
identifiability and stability over time. Because of inter-subject variability in pharmacokinetics 
and metabolism of PET radioligands, a sample size of approximately 12 is required in such 
studies [19-21]. A similar or a little smaller sample size of 10 is often used to measure drug 
occupancy by PET [22]. In order to account for drop-outs, we request a recruitment ceiling of 15 
subjects for each of Phase 2 and 4. To estimate radiation absorbed doses by performing whole 
body imaging, a sample size of about eight is used in many studies. In order to account for drop-
outs, we request a recruitment ceiling of 10 for whole body imaging (Phase 1 and 3 combined). 
 
 
11. Human Subjects Protection 
a. Subject selection 
Participants will be selected based on the study's eligibility criteria. Participants will be 
admitted to the protocol regardless of gender, race, or ethnicity. NIMH employees/staff and their 
immediate family members will be excluded from the study per NIMH policy. 
 
b. Justification for exclusion of children 
 
Because this protocol has more than minimal risk from radiation exposure without 
possibility of direct benefit, inclusion of children is not appropriate. 
 
c. Justification for the exclusion of vulnerable subjects  
Pregnant women will be excluded because this protocol involves exposure to ionizing 
radiation. Lactating women will be excluded because radioisotopes may be excreted in milk.
 
Persons with brain disease and HIV infection are excluded to ensure that the results we 
see are related only to PDE4D and not to another abnormality in the brain, such as diseases that 
are likely to be associated with a disruption of the blood-brain barrier or a viral infection of the 
brain. 
 
d. Justification for sensitive procedures   


 
 
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Not applicable 
 
e. Safeguards for vulnerable populations 
Pregnancy testing will be performed before PET and MRI scanning for any participants 
of child-bearing potential. Per the protocol eligibility criteria, if participants are able to become 
pregnant or father a child, adequate measures to prevent pregnancy must be in place. If 
participants chose to use barrier methods of contraception, the acceptable forms include 
diaphragm, cervical cap, male condom, female condom, and spermicidal foam and sponges. 
Females who say they are post-menopausal will have this status confirmed by a follicle 
stimulating hormone (FSH) test at Screening. In addition, all females must have a negative 
pregnancy test within 24 hours before the first dose of BPN14770 regardless of childbearing 
potential. 
Protections for NIH employees and staff participating in this study include: 1) ensuring 
that participation or refusal to participate will have no effect, either beneficial or adverse, on the 
subject’s employment or position at the NIH, 2) giving employees and staff who are interested in 
participating the “NIH Information Sheet on Employee Research Participation” prior to 
obtaining consent, and 3) ensuring that there will be no direct solicitation of employees or staff. 
This study collects sensitive information. For example, we may collect information on 
drug and alcohol use, medical history and diagnoses. The PI will train study staff regarding 
obtaining and handling potentially sensitive and private information about co-workers through 
staff discussions and written branch/section procedures. 
 
Patient advocate 
A patients’ rights representative is available to participants on this protocol. The 
representative is located in Building 10 and can be reached by phone at 301-496-2626. 
Participants may ask any questions about the study and may withdraw their consent at any time. 
 
f. Qualifications of investigators 
 
Robert B. Innis, MD, PhD – Branch Chief, Molecular Imaging Branch, NIMH/NIH. Dr. Innis 
has more than 25 years’ experience using nuclear imaging. He is a clinical authorized user of 
radioisotopes and a credentialed physician. His responsibilities include study design, recruiting 
healthy subjects, consenting subjects, participating in PET scanning procedures, data analyses, 
and interpretation and publication of study results. 
 
Milalynn S. Victorino, CRNP has been a family nurse practitioner since 2016 and a registered 
nurse since 2002.  She is a credentialed clinician with prescriptive authority at the NIH clinical 
center.  Her responsibilities include screening healthy subjects for research protocols, performing 
history and physicals with subject interviews, and consenting potential research subjects. She 
will also participate in PET scan procedures. 
 
Ms. Desiree Ferraris Araneta, CNRP is a credentialed nurse practitioner. Ms. Ferraris Araneta 
has been a nurse practitioner for more than 15 years and was a nurse prior to that.  She is a 
credentialed clinician at the NIH Clinical Center and has patient care credentials including 
prescriptive authority from the NIH Clinical Center. Her responsibilities include patient 
evaluation and care, consenting subjects, and participating in PET scan procedures.  


 
 
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Dr. Denise Rallis-Frutos, DNP is a credentialed nurse. Dr. Rallis-Frutos is a doctoral research 
nurse specialist and has been an associate investigator with the NIMH since 1996.  Her 
responsibilities include patient evaluation and care, consenting subjects, and participating in PET 
and MRI scanning procedures. 
 
Lora D. Weidner, PhD – Postdoctoral fellow, Molecular Imaging Branch NIMH/NIH. Dr. 
Weidner has her PhD in neuroscience and has 2 years of experience in PET studies at the 
University of Pittsburgh. There she gained experience in the analytical as well as the clinical 
aspects of PET, the latter involving patient interaction. At MIB, her responsibilities include, but 
are not limited to: study design, clinical evaluation of subjects, participating in PET scanning 
procedures, data analyses, and interpretation and publication of study results. Dr. Weidner will 
not obtain informed consent. 
 
 
The Principal Investigator has verified that all individuals working on this protocol 
required to take HRPP training under OHSRP SOP 25 (Training requirements for the NIH 
Human Research Protections Program) have completed all required training. 
 
 
The following study investigators will obtain informed consent: Dr. Innis, Dr. Rallis-
Frutos, Ms. Ferraris Araneta, Ms. Victorino. Study investigators obtaining informed consent 
have completed the NIMH HSPU "Elements of Successful Informed Consent" training. 
 
12. Anticipated Benefit 
This study offers no direct benefit to participants, but is likely to yield generalizable 
knowledge about the density of PDE4D in the brains of healthy volunteers. 
 
13. Classification of Risk 
a. For adults  
This study entails more than minimal risk with no prospect of direct benefit to participants.  
 
b. For adults without consent capacity 
 Not applicable. 
 
c. For children 
 Not applicable. 
 
d. Overall risk and benefit consideration 
The risks are reasonable in relation to the anticipated benefit. 
 
14. Consent Documents and Process 
a. Designation of those obtaining consent 
Study investigators designated as able to obtain consent in section 11f above will obtain 
informed consent. All study investigators obtaining informed consent have completed the NIMH 
HSPU ‘Elements of Successful Informed Consent’ training. Co-workers will not consent each 
other.  
 


 
 
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b. Consent procedures 
All participants will receive a verbal explanation in terms suited to their comprehension 
of the purposes, procedures, and potential risks of the study and of their rights as research 
participants. Participants will have the opportunity to carefully review the written consent form 
and ask questions regarding this study prior to signing. 
 
c. Consent documents 
The consent forms contain all required elements. Each of the four Phases has a separate 
consent form.  
 
15. Data and Safety Monitoring 
a. Data and safety monitor 
This study will be monitored by an independent safety monitor (ISM): Dr. Carlos A. 
Zarate Jr., MD. Dr. Zarate is Chief of the Experimental Therapeutics and Pathophysiology 
Branch and Mood and Anxiety Disorders Research at the NIMH. Dr. Zarate is an internationally 
recognized leader in the clinical neuroscience and experimental therapeutics of mood and anxiety 
disorders, especially the use of glutamatergic agents like ketamine and riluzole in treatment-
resistant unipolar and bipolar depression. He was senior author on one of the first studies 
demonstrating the relationship between ketamine infusion and reductions in suicidal thoughts, 
and has since published over 10 articles related to the neurobiology of suicide risk.  He has a 
strong track record in recruiting, studying and publishing novel research findings and mentoring 
junior colleagues in his area of expertise. His primary responsibility will be to provide 
independent safety monitoring in a timely fashion. 
b. Data and safety monitoring plan 
About every six months, the PI will prepare for the Independent Monitor a report on data and 
safety parameters, including all AEs, SAEs, and protocol deviations. The Independent monitor 
will provide a written monitoring report to be submitted to the IRB at the time of continuing 
review.  
 
c. Criteria for stopping the study or suspending enrollment or procedures 
 
The study will be stopped in the event of a Serious Adverse Event related to research or if 
new data sheds light on the danger of any procedure used on this protocol.  The PI/Independent 
Monitor and IRB will determine if changes are needed for the research to continue or if it will 
be closed. Any changes required as conditions for resuming the research must be submitted as 
an amendment and IRB-approved before the changes can be implemented.  
 
16. Quality Assurance 
a.QA Monitor 
Quality assurance will be monitored by the PI, the research team, and the Office of 
Regulatory Oversight (ORO).  
 
b. QA Plan 
ORO monitors intramural research studies to ensure compliance with GCP, organizational 
policies and regulations. Audit frequency is determined by the ORO SOP based on the study 
level of risk. Results of the ORO audits are provided to the PI, the Clinical Director and the CNS 


 
 
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IRB. As an IND study, this protocol will be subject to GCP audits at study initiation and after the 
first enrolled subject. Timing of subsequent review will be established by the ORO but no less 
frequent than every other year.  
 
17. Reporting of Unanticipated Problems, Adverse Events, and Protocol Deviations 
Reporting of Unanticipated problems, adverse events and protocol deviations 
The Principal Investigator is responsible for detecting, documenting, and reporting 
unanticipated problems, adverse events (AEs), including serious adverse events (SAEs), and 
deviations in accordance with NIH policy, IRB requirements, and federal regulations. 
Relatedness to the research of all serious adverse events will be determined by the PI in 
consultation with the CD. 
Serious unanticipated problems, serious adverse events (including deaths) that are not 
unanticipated problems, and serious protocol deviations will be reported to the IRB and CD as 
soon as possible and in writing not more than 7 days after the PI first learns of the event, unless 
immediate reporting is waived for specific serious adverse events as noted below. Not serious 
unanticipated problems and not serious deviations will be reported to the IRB and CD as soon as 
possible and in writing not more than 14 days after the PI first learns of the event. Written 
reports will be submitted in PTMS. 
All adverse events, deviations, and unanticipated problems will be summarized and 
reported at the time of Continuing Review. 
 
It is anticipated that participants in this study will occasionally miss or fail to complete an 
assessment or procedure, such as a completion of a rating scale or a blood draw, or fail to 
complete a procedure or visit within protocol-specified time frames.  Omissions such as these 
will be considered expected events and not protocol deviations provided they are infrequent and 
do not include data needed to assess safety or the primary study outcome.  Cumulative 
proportions of these missed events in the study population will be presented to the IRB annually. 
In addition, the rate of omissions will be monitored by the Investigators. If an individual misses 
more than 15% of the required assessments/procedures or if more than 15% of the participants 
miss completion of the same assessment or procedure, it will be considered a deviation and a 
deviation report will be sent to the IRB within two weeks.  
If the total number of expected items (study visits, study assessments/procedures) is less 
than 16, then two or more missed items are reportable. If the total number of expected items is 
greater than 16, then, if more than 15% are missed, it is reportable.  
 
 
For 11C-T1650 and BPN14770 Studied under IND 
The PI will immediately report SAEs to the Sponsor according to the requirements of 21 CFR 
312.64(b) and as agreed upon with the sponsor. The PI will record nonserious AEs and report them to the 
Sponsor within 14 days. 
 
 
 
18. Alternatives to Participation 
Subjects do not receive any treatment in this study or forego any treatment in order to 
participate in this study. The alternative, therefore, is not to participate. 
 


 
 
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19. Privacy 
 
All research activities will be conducted in as private a setting as possible 
 
20. Confidentiality 
a. For research data and investigator medical records 
Data will be kept in password-protected computers. Only study investigators will have access to the 
data.  This study collects sensitive medical information. The PI will train study staff regarding 
obtaining and handling potentially sensitive and private information about co-workers through 
staff discussions and written branch/section procedures. 
 
b. For stored samples 
Blood samples to measure 11C-T1650 concentrations will be discarded at the end of the 
PET scan. Blood samples to measure BPN14770 concentrations will be kept in a locked freezer 
of MIB/NIMH in the NIH Bethesda campus. Data will be stored using codes that we assign.  
 
c. Special precautions 
Data will be kept in password-protected computers. Only study investigators will have access 
to the data. 
 
21. Conflict of Interest 
a. Distribution of NIH guidelines 
NIH guidelines on conflict of interest have been distributed to all investigators.  
b.  Conflict of interest  
There are no conflicts of interest to report. 
c. Role of a commercial company or sponsor  
  Tetra Discovery Partners has developed and is providing a new PDE4D selective inhibitor 
BPN14770 and the precursor to synthesize 11C-labeled PET ligand, 11C-T-1650 to NIMH 
without charge. Tetra Discovery Partners will receive information learned in the study, but they 
will not receive any identifying information about the participants. No NIMH investigator 
involved in this study receives any payment or other benefits from Tetra Discovery Partners. 
 
Tetra Discovery Partners intends to supply BPN14770 and 11C-T-1650 and NIMH will 
finance all aspects of the study. The subjects will not bear responsibility for any costs associated 
with study participation 
 
 
22. Technology Transfer 
CTA 2018-0122 with Tetra Discovery Partners has been uploaded in PTMS. 
 
23. Research and Travel Compensation 
Volunteers will be compensated for time and research-related inconveniences. 
Reimbursement is based on NIH standards for time devoted to the research project. Participants 
will be paid for each portion of the study they have completed whether or not they opt for early 
withdrawal from participation. Without any delay of study procedures or unanticipated 
inconvenience, the maximum possible compensation is $940.  If the investigators need to delay 


 
 
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study procedures or if additional time is needed for completion, subjects may receive additional 
compensation in accordance with NIH guidelines. 
Employees and staff who participate during work hours must have permission from their 
supervisor. NIH employees must either participate outside of work hours or take leave in order to 
receive compensation.   
 
Subjects undergoing whole body scan (Phase1 and 3) 
Visit 1 to NIH 
 
PET scanning 
$150 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
 
 
Total 
$200 
 
Subjects Enzyme occupancy brain scans (Phase 2) 
 
Total Pay 
Visit 1 to NIH 
 
MRI 
$100 
Pregnancy test 
$10 
 
 
Visit 2 to NIH 
 
PET scanning 
$150 
Arterial catheter 
$60 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
 
 
Visit 3 to NIH 
 
PET scanning 
$150 
Arterial catheter 
$60 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
BPN14770 administration 
$50 
 
 
Visit 4 to NIH 
 
PET scanning 
$150 
Arterial catheter 
$60 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
 
 
Total 
$940 
 


 
 
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Subjects undergoing Test Retest Brain Scans (Phase 4) 
 
Total Pay 
Visit 1 to NIH 
 
MRI 
$100 
Pregnancy test 
$10 
 
 
Visit 2 to NIH 
 
PET scanning 
$150 
Arterial catheter 
$60 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
 
 
Visit 3 to NIH 
 
PET scanning 
$150 
Arterial catheter 
$60 
Antecubital venous catheters 
$30 
Pregnancy test 
$10 
Movement restriction 
$10 
 
 
Total 
$630 
 
NIH will cover travel expenses to the Clinical Center for all participants in accord with NIH 
guidelines. 
 


 
 
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24. References 
1. 
Fleischhacker WW, Hinterhuber H, Bauer H, Pflug B, Berner P, Simhandl C, et al. A 
multicenter double-blind study of three different doses of the new cAMP-phosphodiesterase 
inhibitor rolipram in patients with major depressive disorder. Neuropsychobiol. 1992;26:59-64. 
2. 
Zhang HT. Cyclic AMP-specific phosphodiesterase-4 as a target for the development of 
antidepressant drugs. Curr Pharm Des. 2009;15:1688-98. 
3. 
Burgin AB, Magnusson OT, Singh J, Witte P, Staker BL, Bjornsson JM, et al. Design of 
phosphodiesterase 4D (PDE4D) allosteric modulators for enhancing cognition with improved 
safety. Nat Biotechnol. 2010;28:63-70. doi:nbt.1598 [pii] 
10.1038/nbt.1598. 
4. 
Zhang HT, Huang Y, Jin SL, Frith SA, Suvarna N, Conti M, et al. Antidepressant-like 
profile and reduced sensitivity to rolipram in mice deficient in the PDE4D phosphodiesterase 
enzyme. Neuropsychopharmacology. 2002;27:587-95. doi:10.1016/S0893-133X(02)00344-5. 
5. 
Engels P, Fichtel K, Lubbert H. Expression and regulation of human and rat 
phosphodiesterase type IV isogenes. FEBS Lett. 1994;350:291-5. 
6. 
Beghe B, Rabe KF, Fabbri LM. Phosphodiesterase-4 inhibitor therapy for lung diseases. 
American journal of respiratory and critical care medicine. 2013;188:271-8. 
doi:10.1164/rccm.201301-0021PP. 
7. 
Park H, No AL, Lee JM, Chen L, Lee SY, Lee DS, et al. PDE4 inhibitor upregulates 
PTH-induced osteoclast formation via CRE-mediated COX-2 expression in osteoblasts. FEBS 
Lett. 2010;584:173-80. doi:10.1016/j.febslet.2009.11.043. 
8. 
Nomura-Furuwatari C, Wakitani S, Hashimoto Y, Imai Y, Ohta Y, Nakagawa K, et al. 
Expression profiles of phosphodiesterase 4D splicing variants in osteoblastic cells. Journal of 
bone and mineral metabolism. 2008;26:152-8. doi:10.1007/s00774-007-0803-7. 
9. 
Zanotti-Fregonara P, Zoghbi SS, Liow JS, Luong E, Boellaard R, Gladding RL, et al. 
Kinetic analysis in human brain of [11C](R)-rolipram, a positron emission tomographic 
radioligand to image phosphodiesterase 4: a retest study and use of an image-derived input 
function. Neuroimage. 2011;54:1903-9. doi:S1053-8119(10)01357-1 [pii] 
10.1016/j.neuroimage.2010.10.064. 
10. 
Fujita M, Zoghbi SS, Crescenzo MS, Hong J, Musachio JL, Lu J-Q, et al. Quantification 
of brain phosphodiesterase 4 in rat with (R)-[11C]rolipram-PET. NeuroImage. 2005;26:1201-10. 
11. 
Itoh T, Abe K, Zoghbi SS, Inoue O, Hong J, Imaizumi M, et al. Positron emission 
tomographic measurement of the in vivo affinity of 11C-(R)-rolipram and the density of its 
target, phosphodiesterase-4, in brain of conscious and anesthetized rats. J Nucl Med. 
2009;50:749-56. 
12. 
Itoh T, Abe K, Hong J, Inoue O, Pike VW, Innis RB, et al. Effects of cAMP dependent 
protein kinase activator and inhibitor on in vivo PET rolipram binding to phosphodiesterase 4 in 
conscious rats. Synapse. 2010;64:172-6. 
13. 
Fujita M, Hines CS, Zoghbi SS, Mallinger AG, Dickstein LP, Liow J-S, et al. 
Downregulation of brain phosphodiesterase type IV measured with 11C-(R)-rolipram positron 
emission tomography in major depressive disorder. Biol Psychiatry. 2012;72:548-54. 
14. 
Tetra-Discovery-Partners. BPN14770 Investigator’s Brochure, Edition 1, October 21, 
2015. 
15. 
Cunningham VJ, Rabiner EA, Slifstein M, Laruelle M, Gunn RN. Measuring drug 
occupancy in the absence of a reference region: the Lassen plot re-visited. J Cereb Blood Flow 
Metab. 2010;30:46-50. doi:10.1038/jcbfm.2009.190. 


 
 
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16. 
Zanotti-Fregonara P, Innis RB. Suggested pathway to assess radiation safety of 11C-
labeled PET tracers for first-in-human studies. Eur J Nucl Med Mol Biol. 2012;39:396-8. 
17. 
Zanotti-Fregonara P, Lammertsma AA, Innis RB. Suggested pathway to assess radiation 
safety of 18F-labeled PET tracers for first-in-human studies. Eur J Nucl Med Mol Imaging 
2013;40:1781-3. 
18. 
Lockwood AH. Invasiveness in studies of brain function by positron emission 
tomography (PET). J Cereb Blood Flow Metab. 1985;5:487-9. 
19. 
Fujita M, Seibyl JP, Verhoeff NPLG, Ichise M, Baldwin RM, Zoghbi SS, et al. Kinetic 
and equilibrium analyses of [123I]epidepride binding to striatal and extrastriatal dopamine D2 
receptors. Synapse. 1999;34:290-304. 
20. 
Ichise M, Liow JS, Lu JQ, Takano A, Model K, Toyama H, et al. Linearized reference 
tissue parametric imaging methods: application to [11C]DASB positron emission tomography 
studies of the serotonin transporter in human brain. J Cereb Blood Flow Metab. 2003;23:1096-
112. 
21. 
Koeppe RA, Frey KA, Snyder SE, Meyer P, Kilbourn MR, Kuhl DE. Kinetic modeling of 
N-[11C]methylpiperidin-4-yl propionate: alternatives for analysis of an irreversible positron 
emission tomography trace for measurement of acetylcholinesterase activity in human brain. J 
Cereb Blood Flow Metab. 1999;19:1150-63. 
22. 
Fujita M, Kobayashi M, Ikawa M, Gunn RN, Rabiner EA, Owen DR, et al. Comparison 
of four 11C-labeled PET ligands to quantify translocator protein 18 kDa (TSPO) in human brain: 
(R)-PK11195, PBR28, DPA-713, and ER176 – based on recent publications that measured 
specific-to-nondisplaceable ratios. EJNMMI Research. In press. 
 
 
 


 
 
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25. Attachments 
 List of P450 inhibitors 
 
26. Consent Forms 
 Phase 1: For the first healthy subject who has a whole body scan 
 Phase 2: Healthy subjects who have three brain scans 
 Phase 3: Additional healthy subjects who have a whole body scan 
 Phase 4: Healthy subjects who have two brain scans