Clinical trial NCT03106740
Conditions: Low Back Pain Back Pain With Radiation Back Pain Without Radiation Back Pain Lower Back Chronic Back Ache Pain, Chronic
Keywords: Microglia Minocycline Magnetic Resonance Imaging Positron Emission Tomography Pain Astrocytes Glia Human Back Pain
Sponsor: Marco Loggia
Start date: 2017-10-10; Completion date: 2024-04-30
Enrollment: 60 participants; Allocation: RANDOMIZED; Intervention model: PARALLEL

Brief summary:
In this research, the study team will use brain imaging to evaluate the presence of neuroinflammation in the brains and spinal cords of patients with low back pain. The efficacy of minocycline use for low back pain treatment will also be evaluated by observing whether short-term minocycline administration will reduce neuroinflammation and low back pain symptoms.

Detailed description:
The goal of this research study is to evaluate whether the central nervous systems of those with low back pain are different from those of healthy, pain-free individuals. Specifically, the researchers will test whether "glial cells" (the immune cells of the brain and spinal cord) are more active in patients with low back pain than in healthy volunteers. The investigators' previous study showed that patients with chronic low back pain demonstrated elevations in brain levels of the 18kDa translocator protein (TSPO), a marker of glial activation.

To test this hypothesis, the study team will image the brains and spinal cords of patients suffering from low back pain using integrated magnetic resonance- positron emission tomography (MR-PET), and a radiotracer called \[11C\]PBR28, which tracks levels of glial activation.

The efficacy of minocycline as a treatment for chronic low back pain will also be evaluated. A recent study demonstrated a statistically significant reduction in pain in those with lumbar radiculopathy after treatment with minocycline, leading the investigators of this study to believe that minocycline may have potential efficacy in treating other back pain populations.

The study team will observe whether a short course of minocycline hydrochloride may reduce glial activation along with self-reported low back pain symptoms. To this end, patients will be evaluated clinically and/or re-scanned after completing a 2-week trial of minocycline or placebo (a sugar pill).

This study will be enrolling individuals who have been suffering from sub-acute (short-term) and chronic low back pain.

Arms: arm 1: Evaluation with Magnetic Resonance-Positron Emission Tomography Imaging and/or behavioral pain assessment before and after a 2-week trial of Minocycline Hydrochloride, 100mg capsule arm 2: Evaluation with Magnetic Resonance-Positron Emission Tomography Imaging and/or behavioral pain assessment before and after 2 weeks of treatment with a placebo capsule.
Interventions: intervention 1: Minocycline Hydrochloride 100mg Capsule intervention 2: Magnetic Resonance-Positron Emission Tomography Imaging intervention 3: Placebo Capsule
Intervention descriptions: intervention 1: Minocycline 100mg will be administered by mouth daily for 2 weeks intervention 2: Up to 15 millicuries of \[11C\]PBR28 will be administered to each subject at each imaging visit, for a maximum of 2 imaging visits. intervention 3: 1 Placebo Capsule (compounded with lactose powder) will be administered by mouth daily for 2 weeks

Protocol documents:
Prot_SAP_000.pdf: 
Evaluating the Role of Neuroinflammation in Low Back Pain
NCT03106740
Version Date: May 12, 2022


Institutional Review Board
Intervention/Interaction Detailed Protocol
Principal Investigator:
Project Title:
Version Date:
Marco Loggia, PhD
Imaging Glia-mediated NeuroInflammation and Treatment
Efficacy (the IGNITE study)
5/12/2022
1.
Background and Significance
Millions of individuals suffer from chronic pain
Chronic pain is defined as pain without apparent biological value that has persisted beyond the
normal tissue healing time (usually taken to be 3 or 6 months 1,2). Chronic pain is a widespread
public health issue 3, and its prevalence is enormous. The weighted mean prevalence of chronic
pain in the general population has been estimated by some at 35.5%, or 105 million, in the
United States 4. Not only does chronic pain affect both physical and mental functioning, thus
compromising quality of life; it is also associated with astronomical costs. In addition to the
direct costs of treating pain—including health care for diagnosis and treatment, drugs, therapies,
and other medical expenses—chronic pain results in lost work time and reduced productivity 5,6.
Past estimates of the annual cost of chronic pain in the United States, including healthcare
expenses, lost income and productivity, were close to $100 billion 7.
Treatment for chronic pain is unsatisfactory
Despite the enormity of the phenomenon, clinical needs for chronic pain are largely unmet. The
treatment of choice for the largest majority (as many as 90% 8) of patients seeking chronic pain
management is based on opioid analgesics. However, the evidence supporting long-term
effectiveness of opioid drugs in relieving pain and improving functional status is weak 9. For
instance, despite the widespread use of opioids for palliative care, more than half of all
hospitalized patients experience pain in the last days of their lives, and 50-75% of cancer patients
die in moderate to severe pain 10.
The current opioid-based pharmacological approaches to treat chronic pain are not only
ineffective, but they generally have multiple unpleasant side effects, including constipation,
pruritus, respiratory depression, nausea, vomiting, hyperalgesia, dizziness, sedation 9, as well as
abuse and dependence 8,11,12. Taken together, the unsatisfactory treatment efficacy and the
occurrence of significant side effects, clearly stress the importance of achieving a deeper
understanding of the pathophysiological mechanisms underlying chronic pain, in order to
eventually identify viable treatment options alternative to ones currently available.
Microglia and pain
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One of the reasons for the poor efficacy of the treatment options currently available for chronic
pain might be that these are primarily aimed at suppressing neuronal activity within nociceptive
pathways of the nervous system. However, it is now increasingly clear that neurons are far from
being the only players that drive the establishment and/or maintenance of clinical pain
symptoms. Rather, evidence from animal studies now suggests a central role of glial cells in the
nervous system, including microglia 13,14.
Microglia are a subpopulation of macrophages that rapidly activate in response to a variety of
pathological conditions 15, including persistent pain 16-23. Microglial activation (MA) is
characterized by a stereotypic pattern of cellular responses, including specific morphological
changes, proliferation, increased or de-novo expression of cell surface markers or receptors, and
migration to the site of injury 24. MA generally represents an adaptive homeostatic defense
response which enables the destruction of invading micro-organisms, the removal of potentially
deleterious debris as well the promotion of tissue repair. However, animal studies have now
showed that the uncontrolled activation of microglial cells under pathological pain conditions
induces the release of substances that can sensitize pain pathways, such as proinflammatory
cytokines, complement components, and others 25. While evidence of pain-related MA was
originally observed in the spinal cord, more recently it was also discovered at the level of the
brain, including in the rostral ventromedial medulla 20,26, the trigeminal nuclear complex 19,27,
and the ventral posterolateral nucleus of the thalamus 28,29.
While most of the evidence on the occurrence of pain-related glial responses in the central
nervous system comes from animal studies, a few important observations indicate that similar
phenomena should occur also in humans 13. First, immunohistochemical markers of microglial
and astroglial activation have been detected in the spinal cord of a patient with chronic regional
pain syndrome in a postmortem study 30. Furthermore, an increase in the concentration of the
glial marker s-100β was reported in the cerebrospinal fluid of patients with lumbar disc
herniation and in the serum of children with recurrent headaches 31,32. Finally, a positron
emission tomography (PET) study has revealed that human subjects with neuropathic pain
secondary to peripheral nerve damage express increased thalamic binding for [11C](R)-PK11195
33, an in vivo marker of microglial cell activation 34,35.
Recently, our group has also shown that patients with chronic low back pain (cLBP) have
increased brain levels of the 18kDa translocator protein (TSPO), a marker of glial activation36. In
addition, preliminary data collected from a different cohort of patients with cLBP and sciatica
suggest an increase in spinal cord TSPO levels. Together, these results suggest that human
chronic pain conditions are likely to be associated with a glial reaction, both in the spinal cord, as
well as in the brain.
In the present study, we propose to test a model built upon observations from our own human
data as well as from the animal literature, which describes the temporal dynamics, spatial extent,
somatotopic specificity, and clinical significance of glial activation in humans with low back
pain. According to this model, glial activation: (1) originates during the acute or subacute stage
in the central nervous system sites most proximal to the back (i.e., spinal cord); (2) propagates
trans-synaptically26,27 up to the brain, with increasing pain duration and (3) presents a
somatotopic organization in the brain (in the primary somatosensory and motor cortices; S1/M1),
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which reflects the bodily distribution of patients’ pain symptoms. Finally, the model predicts that
(4) pharmacological glial inhibition reduces pain and that (5) the presence of glial activation in
the subacute stage predicts transition to chronic pain.
In order to test this model, we will study patients with subacute (pain duration 1-4 months) and
chronic (pain duration > 6 months) low back pain longitudinally. Most participants will be
studied before and after a treatment with minocycline or placebo. In animal models minocycline
is commonly used as a glial inhibitor, including in preclinical models of pain25. Minocycline is
readily absorbed by the gastrointestinal tract and easily crosses the blood-brain barrier37,
reaching cerebrospinal fluid levels of around 25%- 30% of serum concentration38. In humans
with subacute lumbar radiculopathy, minocycline was shown to induce a small but statistically
significant reduction in pain39, however it is unclear whether it reduces glial activation in
humans.
2.
Specific Aims and Objectives
Aim 1. Assess spatial extent and and somatotopic organization of glial activation in chronic
LBP
Hypothesis 1.1. The cLBP group will demonstrate higher PET signal in the brain (thalamus,
S1/M1 representation of the lumbar spine), thus corroborating our previous observations36 in a
larger sample, as well as in the lower lumbar/upper sacral spinal cord segments (situated at the
T11-L1 vertebral levels).
Hypothesis 1.2. Patients with radicular cLBP (i.e., pain in the back, shooting down the leg below
the knee), but not those with axial cLBP (i.e., pain in the back only), will demonstrate an
additional PET signal increase at the level of the S1/M1 representation of the leg, in the
paracentral lobule. This observation will provide evidence for somatotopic organization of glial
activation in the brain of cLBP patients.
Aim 2. Assess temporal evolution of glial activation in subacute LBP
Hypothesis 2.1. In the sLBP group, the spinal PET signal (but, unlike in the cLBP group, not the
brain signal) will be higher than in healthy controls. This observation will provide evidence of
spinal glial activation in sLBP, and indicate that chronicity of pain is needed for glial activation
to occur in the brain.
Hypothesis 2.2. The baseline spinal PET signal will be heightened in sLBP patients who
eventually transition to cLBP, but not in sLBP patients who subsequently heal. This observation
will suggest that spinal glial activation is a predisposing factor for pain chronification.
Aim 3. Assess the effect of minocycline on glial activation and pain, and the role of
minocycline as predictor of response to minocycline
Hypothesis 3.1. On average, a 2-week treatment with the glial inhibitor minocycline, compared
to the placebo group, will reduce pain and [11C]PBR28 PET signal.
Hypothesis 3.2. Higher pre-treatment glial activation will predict larger behavioral and imaging
responses to minocycline.
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3.
General Description of Study Design
In brief, the structure of the study will be as follows (see Figure 1):
Figure 1. Study schema
-CLBP arm: After a behavioral visit aimed at determining eligibility, 50 cLBP patients
will be randomized to receive either Minocycline 100mg (N=25) or Placebo (N=25).
Following randomization, subjects will then participate in their first imaging visit, during
which they will undergo a simultaneous MR-PET scan. At this visit, subjects who are
assigned to the clinical trial groups will also receive the treatment corresponding to the
group to which they are assigned. During the drug trial period, subjects will also be sent a
daily survey to assess the treatment effect of the medication on their pain. As soon as
possible after the end of the 2-week drug trial period, all subjects will be scanned again.
-SLBP arm: After a behavioral visit aimed at determining eligibility, 50 sLBP patients
will be randomized to receive either Minocycline 100mg (N=25) or Placebo (N=25).
Following randomization, all subjects will then participate in an imaging visit (at 1 to 4
months after reported pain onset), during which they will undergo a simultaneous MR-
PET scan. At this visit, subjects who are assigned to the clinical trial groups will also
receive the treatment corresponding to the group to which they are assigned. During the
drug trial period, subjects will also be sent a daily survey to assess the treatment effect of
the medication on their pain.
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All sLBP patients will be sent a survey once per week to assess the status of their pain and track
any interventions they receive. These patients will be re-evaluated clinically at 6 months post-
pain onset.
4.
Subject Selection
We plan to identify 50 patients with subacute low back pain (sLBP; i.e., with a pain duration
between 1 to 4 months at time of behavioral screening), as well as 50 patients with chronic low
back pain (cLBP; i.e., with a pain duration longer than 6 months), who will complete the study.
In order to achieve the final sample size of 100 study completers, we will consent up to a total of
175 participants, in order to account for screen fails and attrition.
We are not planning to enroll subjects from at-risk populations (e.g., children and minors,
cognitively impaired persons, prisoners). Written informed consent form will be obtained in all
cases.
Inclusion Criteria for sLBP:
-
age ≥ 18 and ≤ 75;
-
the ability to give written, informed consent;
-
fluency in English;
-
Subacute low back pain, ongoing for 1-4 months prior to enrollment with ongoing
pain that averaged at least 4, on a 0-10 scale of pain during a typical week, and
present for at least 50% of days during a typical week;
-
Medical records confirming diagnosis of low back pain; however, subjects can be
exempted from providing medical records if sufficient evidence for low back pain
is found upon clinical evaluation.
Inclusion Criteria for cLBP:
-
age ≥ 18 and ≤ 75;
-
the ability to give written, informed consent;
-
fluency in English;
-
Chronic low back pain, ongoing for at least 6 months prior to enrollment, with
ongoing pain that averaged at least 4, on a 0-10 scale of pain during a typical
week, and present for at least 50% of days during a typical week;
-
on a stable pain treatment (pharmacological or otherwise) for the previous four
weeks;
-
Medical records confirming diagnosis of low back pain.
Exclusion Criteria for sLBP:
-
any interventional pain procedures during the 2-week drug trial period or between
the first scan visit and completion of the drug trial period;
-
contraindications to fMRI scanning and PET scanning (including presence of a
cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular
clips in the head or previous neurosurgery, prosthetic heart valves,
claustrophobia);
-
History of disease that may be exacerbated by minocycline administration i.e.
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Clostridium Difficile colitis, lupus, or vasculitis;
-
any history of neurological illness or major medical illness affecting the central
nervous system;
-
current or past history of major psychiatric illness;
-
PTSD, depression, and anxiety are exclusion criteria only if the conditions
were so severe as to require hospitalization in the past 5 years;
-
peripheral neuropathic pain of greater severity than that of the back pain;
-
pregnancy or breast feeding;
-
history of head trauma requiring hospitalization;
-
history of impaired elimination or abnormal kidney function testing (e.g., renal
insufficiency with GFR < 60);
-
history of diagnosed liver disease or abnormal liver function testing within the
past 6 weeks (e.g. total protein, albumin/globulin ratio, bilirubin, or alkaline
phosphatase levels falling outside of normal ranges);
-
routine use of benzodiazepines or any use in the past 2 weeks except clonazepam
(Klonopin), lorazepam (Ativan), and alprazolam (Xanax);
-
current bacterial or viral infection;
-
Contraindications to minocycline administration including:
-
Allergy to minocycline or other tetracycline medications;
-
Taking medications known to interact with minocycline including:
anticoagulant therapies; penicillin; antacid medications containing:
aluminum, calcium, magnesium, or iron; methoxyflurane; isotretinoin;
ergot alkaloids or their derivatives; or any other drugs determined by the
study physician to be unsafe, taken in concomitance with minocycline;
-
Any other contraindications to minocycline administration noted by the
study physician;
-
History of COVID-19 infection within the past 3 months WITH neurological
symptoms that required hospitalization.
Exclusion Criteria for cLBP are the same as for sLBP, with the addition of:
-
outpatient surgery within 2 months and inpatient surgery within 6 months from
the time of scanning;
-
epidural steroid injections within 6 weeks prior to scanning procedure or at any
point during study enrollment;
-
surgical intervention or introduction/change in opioid regimen at any point during
study enrollment;
-
current or past history within the last 5 years of major medical illness not
affecting the central nervous system, other than chronic pain;
-
peripheral nerve injury;
-
major cardiac event within the past 10 years;
-
any use of recreational drugs in the past 6 months;
-
marijuana use, medical or recreational, is an exclusion only if average use
exceeds 1x/week;
-
an abnormal physical exam (e.g., peripheral edema);
-
routine use of opioids ≥ 60 mg morphine equivalence;
-
history of substance abuse;
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-
use of immunosuppressive medications, such as prednisone, TNF medications
within 2 weeks of the visit.
Additional Exclusion Criteria for sLBP only:
-
a separate episode of back pain within the same year, lasting at least 1 month and
requiring medical attention;
-
epidural steroid injections within 6 weeks prior to scanning procedure or during
the 2-week drug trial period;
-
Surgical intervention or introduction/change in opioid regimen during the 2-week
drug trial period.
Exclusion Criteria for placement of arterial line (sLBP and cLBP):
-
contraindications to placement of arterial line, such as abnormal result on
modified Allen’s test on both hands; Raynaud syndrome; bleeding disorder; use
of anticoagulants such as Coumadin, Plavix or Lovenox.
5.
Subject Enrollment
Subjects will be recruited through advertising by flyers and printed announcements posted within
as well as outside of our Partners community. In addition, email, web and bulletin board
announcements posted in the community will be used. To recruit subjects, we will also use
multiple research databases such as the Partners’ RSVP for Health system, Partners Clinical
Trials, ResearchMatch, EPIC, and RPDR. We will run queries on EPIC and RPDR to find
subjects with low back pain. Subjects identified through these mechanisms will receive a
recruitment letter in the mail from the Principal Investigator. In addition, methods that advertise
the study to the greater community will be used such as Craig’s List, social media posts, posting
flyers on community billboards in the greater Boston area, emails to physicians and family
medicine centers, and advertisements in newspapers etc. will be adopted. Advertisements will
briefly describe the study and invite subjects to call if they are interested. All subjects will
undergo a telephone screening to attempt to distinguish potential subjects from those not meeting
eligibility criteria. Finally, we will be collaborating with a research team at the Emergency
Department in the Brigham and Women’s Hospital, the Phyllis Jen Center for Primary Care at
Brigham and Women’s Hospital, the Walk-In Clinic at MGH, etc. who will help us identify
potential participants for the study. The personnel in those clinics will ask the patients if they are
interested in hearing about our study, and obtain their permission for study staff to approach
them in the waiting rooms to discuss it.
All subacute low back pain subjects will undergo a telephone screening to attempt to distinguish
potential subjects from those not meeting eligibility criteria. For acute low back pain patients, the
BWH ED staff will explicitly ask for their permission to receive an email communication
containing the REDCap Pain Catastrophizing Scale survey from our team. We will use “send
secure” to deliver these emails, if requested by the potential participants. The objective of this
survey will be to identify potential candidates for our study based on their perceptions of pain.
Informed consent will be obtained from all subjects before initiating any study procedures at
study visit #1 (Behavioral visit).
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During screening, potential participants will be fully informed of the purpose and activities
involved in the research study. Interested subjects will be scheduled for an in-person visit where
written informed consent will be immediately obtained, prior to initiating any of the study
procedures. One copy of the signed consent form will be given to the patient and one will be kept
in the study files for documentation. No time limits will be imposed on the informed consent
process. Participants will be permitted to take as much time as they desire to engage in the
informed consent process; any and all of their questions will be answered. It is anticipated that
obtaining written informed consent will take approximately 15-25 minutes, on average.
Comprehension of the consent information will be assessed via solicitation of answers to
questions throughout the process. If comprehension appears to be limited, participants will be
actively queried to determine whether they need further explanation.
A physician member of the staff or a Nurse Practitioner will obtain informed consent, as in all
other protocols involving [11C]PBR28 PET/MR scanning (e.g., 2011P002311).
6.
STUDY PROCEDURES
Screening visit: Subjects eligible to participate will be recruited to participate in a 2-hour
characterization and training session. In this session, we will obtain a signed consent form from
the subjects, explain the procedures involved in the experiment, and administer some or all of the
following validated assessments. We will also collect data on demographics and socioeconomic
status. Computer-based tasks will be completed on a laptop. All assessments, including those
involving experimental noxious stimuli, will be performed by fully trained study staff members
such as post-doctoral research fellows and Clinical Research Coordinators, under the supervision
of and periodic monitoring by the Principal Investigator (PI), who has ample experience in, and
familiarity with, the use of experimental pain stimuli in research studies.
Many of these assessments are already in use in one or more IRB approved protocols (e.g.,
2011P002311).
Hospital Anxiety and Depression Scale (HADS): The HADS is a 14-item self-report survey
designed for populations with medical illness40. It does not include somatic symptoms, such as
fatigue and sleeplessness, which may otherwise be attributable to pain. It asks patients to rate
depression and anxiety symptom over the past week on a 4-point Likert scale. It has been
validated in several medical illness populations and has been used extensively in chronic pain
patients.
The Pain Catastrophizing Scale (PCS): It is a 13-item self report scale which measures pain-
related Rumination, Magnification and Helplessness41.
PainDETECT42: The PainDETECT is a screening questionnaire used to estimate the likelihood
of a neuropathic component in chronic pain.
Social Provisions Scale (SPS): The social provisions scale measures the social support provided
by the patient’s current relationships.43
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Adverse Childhood Experiences Scale (ACE): The ACE scale asks about 10 common adverse
events/experiences that affect development such as childhood maltreatment, parental divorce,
and parental incarceration. Increased ACE scores have been associated with negative health
outcomes such as shortened life span, mental illness, and chronic illness.44
Brief Trauma Questionnaire (BTQ)45,46 : The BTQ will be used to determine whether an
individual meets Criterion A1 for traumatic exposure according to the DSM-V PTSD diagnosis.
It is a brief self-report questionnaire designed to assess 10 traumatic events including physical
assault, car accidents, natural disasters, and unwanted sexual contact. It is derived from the Brief
Trauma Interview.
Snaith-Hamilton Pleasure Scale (SHAPS)47: The Snaith-Hamilton survey is a 14-item
questionnaire designed to estimate the degree to which an individual is able to experience
pleasure, or the anticipation of pleasure. The questionnaire assesses four domains of hedonic
experience: interest/pastimes, social interaction, sensory experience, and food/drink. All items
relate to daily experiences encountered by most people.
Fibromyalgia Survey Questionnaire (FSQ)117: The Fibromyalgia Survey Questionnaire is a 5-
item questionnaire that is aimed at assessing the presence of fibromyalgia, or pain centralization,
subclinically in people who do not meet the fibromyalgia criteria.
Thermal stimuli: We will also test for participants’ sensitivity to cool/warm and painful stimuli.
Brief (1-15s) thermal stimuli will be delivered from a neutral baseline temperature (e.g., 32-
38°C) to different part of the body (back, leg, and/or arm) using a computer-controlled system
(Medoc Pathway). Subjects will be asked to rate the intensity of each stimulus using various
scales (e.g., a scale of 0 to 10). These procedures will improve the characterization of our patient
population, as they will allow us to assess whether the degree of ‘central sensitization’ will be a
predictor of symptom characteristics. Similar procedures are used in many other studies of
chronic pain patients, including in studies approved by the Partners IRB (e.g., # 2010P000978,
2015P001150 and 2015P002373, PIed by our colleague Robert Edwards).
Electrical Stimulation: Electrical stimulation will be applied to the back and legs, using
electrodes connected to a muscle/nerve stimulator. The frequencies will elicit different levels of
tolerable stimulation at both non-painful and painful levels, following the procedures similar to
those used in our center’s protocols (e.g., 2011P001364). We will give several stimuli at
precisely controlled current intensities, within a safe and tolerable range, to test for the
participants’ sensitivity to pain and to identify appropriate stimulus intensity to be used to
produce a moderately painful percept in the imaging visit. During the behavioral visit, we will
present up to 25 stimuli, each lasting a maximum of 3s, plus 1-2 stimuli lasting a maximum of
10s, per body site.
History and physical examination: an MD or NP will also collect medical history and perform a
formal physical examination, including a modified Allen’s test to evaluate safety of the arterial
line (a-line) placement and the recording of vital signs (heart rate, blood pressure, and body
temperature).
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Blood and saliva tests: a trained member of the study staff will draw venous blood (up to 10 ml)
from all subjects considered for potential participation in a [11C]PBR28 scan in order to have
them genotyped for the Ala147Thr TSPO polymorphism in the TSPO gene (rs6971) (unless
this genotype information is already available). In addition, up to 50 participants may be
asked to provide a saliva sample. This dual collection of samples will allow us to validate the
genotyping results using DNA extracted from saliva, and may in the future render blood draws
unnecessary for the purpose of genotyping.
While [11C]PBR28 has the advantage of binding to the TSPO protein with a higher ratio of
specific-to-nonspecific binding than [11C](R)PK1119549, it also presents a potential limitation, in
that about 10% of human subjects show no binding to PBR2850 (whereas [11C](R)-PK11195 has
never been associated with non-binding51). A recent study has demonstrated that the rs6971
polymorphism predicts PBR28 binding affinity in human platelets52. Since the low-affinity
binder phenotype is consistent across all tissues within the same subject 51, testing for the
Ala147Thr polymorphism has been suggested to predict low affinity for [11C]PBR28 in all
organs, including the brain. High or Mixed affinity binders (Ala/Ala or Ala/Thr) will be
considered eligible, whereas the Low affinity binders (Thr/Thr) will be considered
ineligible for the [11C]PBR28 PET scan(s). Under special circumstances, some patients may be
scanned before the genotyping results become available to us, as we currently do for one of our
protocols (2014P001709, 2016P001009; PI: Loggia). We would do so if having to wait for the
genotype information to become available could compromise participation or completion of the
study (for instance, if a subacute patient at the time of screening were about to fall out of the 1 to
4 -month window from pain onset, or if a patient had a surgical or other procedure scheduled in
the immediate future that would conflict with the study). The MGH lab responsible for
genotyping typically runs the genotyping assay only twice per month, requiring that we normally
schedule screening and scanning visits approximately two weeks apart.
Of the small number of participants that we anticipate needing to scan without prior genotyping,
only about 10% will be low affinity binders. In addition, having some low affinity binder
participants may allow us to perform sub analyses that will determine whether excluding these
participants is the most appropriate strategy, rather than modeling genotype as a covariate in our
analyses. Should a low affinity binder be scanned under such circumstances, their data will still
provide useful information regarding the distribution of the PET signal across genotypes.
An additional 10 mL of venous blood will be collected and stored for future investigations on the
roles of genetic, molecular, and cellular factors in pain disorders. This will include the future
possibility to generate induced pluripotent stem cells (iPSCs) from peripheral blood mononuclear
cells53-55 to assess in-vitro alterations in patient-derived neural or glial cells56,57.
Urine drug test: We will also perform a urine test to screen for use of opioids and illicit drugs
(including amphetamine, barbiturates, cocaine, marijuana, etc), as well as to monitor urine
riboflavin levels to aid in the assessment of trial compliance. The urine drug screen will be
performed during the screening visit and on the day of the scan. A rapid urine drug screening that
utilizes monoclonal antibodies to detect elevated levels of specific drugs in urine, will be used
for this purpose. Results will be read five minutes after the test was started. Riboflavin will be
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measured using a UV light to detect for the baseline and post-treatment changes in riboflavin
excreted through the urine. This will allow us to measure compliance with the prescribed
treatment regimen.
Following the screening visit, all participants will receive daily web-based surveys, to assess
their pain prior to treatment. These surveys will be administered for 7 days prior to the
commencement of the assigned study treatment. If the treatment needs to be rescheduled, then
the surveys will be restarted 7 days prior to the new start date.
Follow up behavioral visits:
For all sLBPs, some of the assessments listed as part of the screening and imaging visits will be
performed at the follow-up behavioral visit (see ‘Behavioral visit 2’ in Figure 1) along with
blood tests to measure changes in the levels of various substances in the blood, such as the
proinflammatory cytokines IL-6 and TNF-alpha. Up to 15mL of blood will be drawn at the
follow up visit.
In order to comply with public health efforts to address COVID- 19, virtual visits may be
conducted as necessary. Virtual visits will be conducted via MGB approved platforms (i.e. video
calls over Zoom and phone conferences via Doximity Dialer) and will mirror in-person visits
with the identical personnel present as explained above. All questionnaires typically collected
during the in-person behavioral visit may be collected during the remote behavioral visit, as they
are largely already completed on secure online platforms (i.e. StudyTrax). All behavioral visit
study procedures may be performed during the remote behavioral visit, with the exception of the
urine drug test, physical exam, and extensive back pain exam which will be performed at the first
in-person visit (i.e. first imaging visit). When electronic written consent is obtained via REDCap,
the REDCap e-consent template being utilized is equivalent to written consent and is FDA
compliant.
Blood may be drawn for SARS-CoV-2 antibody serology testing, and the presence of antibodies
will be used to explore the possible effects of prior exposure to the coronavirus on
neuroinflammation, in exploratory analyses. Up to 10 ml of blood will be drawn for this purpose.
This testing will be performed through a third party vendor or through the MGH core lab.
MR-PET visit(s)
Participants eligible to continue into the study based on the screening visit and initial
blood/saliva test will be asked to participate in a first MR-PET visit.
Prior to each scan session, subjects will complete screening checklists for MRI and PET. These
checklists will ask the patients whether they have any contraindications for MR or PET scanning.
Female participants of childbearing age will be asked to have ~3mL of their blood drawn in
order to perform a serum pregnancy test on the day of the scan (blood will be sent to the core lab
for super stat testing). In addition, a urine drug test will be repeated on the day of each MR-PET
visit. Subjects who are participating in the treatment arms of the study will also have their urine
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tested with a UV light to detect for the presence of riboflavin. This will allow us to know
whether subjects complied with their prescribed drug regimen.
At the beginning of the scan session, an intravenous catheter will be placed in the participant’s
antecubital vein of the left or right arm, prior to going to the scanning area. Blood will be drawn
to evaluate the circulating level of on interleukins, TNF-alpha, other inflammatory markers, for
protein binding analysis, for SARS-CoV-2 antibody serology testing, and for other serum and
cell processing (e.g. PBMC, PaxGene, TruCulture). During the first scanning visit, up to 55 mL
of blood may be drawn for this purpose. During the second scanning visit, up to 30 mL of blood
may be drawn for this purpose. If applicable, female participants will also be asked how many
days after onset of menses they are on the day of the scan, and the information will be used for
the blood analyses.
Subjects will be instructed to remain still, with eyes open, for the total duration of the scans,
except when prompted to express various ratings (e.g., pain intensity, unpleasantness, anxiety),
or while engaged in any experimental tasks. The radioligand [11C]PBR28 will used to determine
whether patients with chronic pain exhibit evidence of microglial activation.
Following procedures identical to those adopted in other PET studies (including using
[11C]PBR28) from our center (2015P001594, 2013P001297, 2011P001546, 2011P002311,
2016P001009, etc), an arterial line will be placed in a radial artery with local anesthesia (20 or
18 gauge cannula, 2-5 ml of lidocaine 1% intradermal and subcutaneous) using sterile
techniques, if the participant has consented to this procedure. The placement of an arterial line
will be presented as optional to the participants, and we will ask for the participants’ consent
each time. The arterial line will be placed in the arm contralateral to the intravenous line that is
used for the [11C]PBR28 radiotracer injection. The arterial line will enable blood sampling (1mL
to 12mL) at various times during the imaging study for at most 160 mL of blood. The collected
arterial blood will be used to compute metabolite-corrected arterial input function for kinetic
modeling analyses (see Data Acquisition and Analyses). The catheter will be placed by an
individual with anesthesia training(i.e., board-certified anesthesiologist, fully licensed anesthesia
resident, or a certified registered nurse anesthetist), monitored throughout and accessed by an
experienced research nurse. The catheter will be discontinued at the end of the study by a
physician, a nurse practitioner, or a certified registered nurse anesthetist.
Of note, over the course of the three visits, up to 385 mL over three possible visits. This includes
160 mL from the arterial line for each scan and from the IV catheter up to 45 mL at the first scan
and up to 20 mL at the second scan.
During the scan visit, subjects may be asked to complete one more time some or all of the
assessments completed during the screening visit. In addition, subjects may be asked to complete
a few additional assessments including BPI, PROMIS-29, the Trail Making Test, Part B and the
Rey-Osterrieth Complex Figure.
Brief Pain Inventory (BPI): The BPI is a 15-item questionnaire assessing pain location, and 0–10
ratings of pain intensity, relief, quality, pain-related quality of life, and function. It has been
validated in cancer and noncancer pain conditions58.
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Beck Depression Inventory (BDI): The 21-item BDI has shown good sensitivity and specificity
for major depression in chronic pain patients.
Patient Reported Outcomes Measurement Information System (PROMIS-29) questionnaire59:
The PROMIS-29 is a 29-item self-report measure assessing physical, mental, and social health.
Post-Lockdown Impact Survey: This survey will be used to assess patient wellbeing between the
beginning of the pandemic and the date of their scan.
Trail Making Test, Part B60: The Trail Making Test, Part B is a common neuropsychological
assessment used to gauge a participant’s cognitive flexibility and working memory. Participants
are asked to trace a series of numbers and letters around a paper in the proper sequence (i.e. 1-A-
2-B). Participants are timed while they trace from the start of the sequence until they reach the
end of the sequence. If a participant makes an error in the sequence, they will be asked to return
to the last correct point, and start again from there while the time continues to be recorded.
Rey-Osterrieth Complex Figure61,62: The Rey-Osterrieth Complex Figure is another common
neuropsychological assessment used to gauge a participant’s visual and executive functioning.
Participants are shown a picture of an abstract figure. The figure is then removed and participants
are asked to draw the figure from their memory. Participants are again asked to draw the figure
following a 2 minute delay. Participants are scored based on the accuracy of their representation
as compared to the original figure and their approach to the drawing.
During the scan, participants may be asked to complete the Monetary Incentive Delay (MID)
task. The MID task features balanced incentive delivery and analytic strategies designed to
identify activity specific to anticipation or consumption of incentives. The structure of the MID
paradigm will be as follows: Individual trials begin with presentation of one of three visual cues
(0.5 s) signaling potential trial outcomes (reward: +$; loss: -$; no-incentive: 0$). Following a
jittered ISI (approximately 3s), a red square target stimulus will be presented; participants are
instructed to respond to the target with a button press. Following a second ISI (approximately
3s), visual feedback (1.25 s) will be provided. In the reward condition, successful trials are
associated with monetary gains ($1.96 to $2.34) whereas unsuccessful trials lead to no change. In
the loss condition, successful trials are associated with no change whereas unsuccessful trials are
associated with monetary penalties (-$1.81 to -$2.19). No feedback about cumulative earnings
will be provided. Intertrial intervals (ITIs) will be approximately 3s. The task will include up to
five blocks of up to 24 trials (8 reward, 8 loss, 8 no-incentive). Thus, up to 40 trials/ condition
will be available for the analyses of anticipatory activation, whereas up to 20 trials/condition will
be used for post-feedback responses. Participants will be told that faster reaction times (RT) will
increase the likelihood of obtaining rewards and avoiding losses. RT data in three independent
control samples confirmed that the task induces motivated responding: mean RT was fastest on
reward trials, intermediate on loss trials, and slowest on no-incentive trials (all ps<.001; 63 64 ).
In addition, during the scan subjects may receive electrical stimuli similar to those received in
the behavioral visit. This stimulation paradigm, will allow us to assess the relationship between
brain activation in response to acute pain and neuroinflammation. The subjects who will receive
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electrical stimuli will be chosen based on several considerations, including how well the subject
has tolerated these stimuli during the behavioral visit.
Vital signs (heart rate, blood pressure, and body temperature) will also be recorded for all
subjects before and after [11C]PBR28 injection to monitor for any adverse events related to
radioligand administration. For subjects in the cLBP groups the pre-administration vital signs
will also be compared between imaging visit 1 and imaging visit 2 to assess for significant
deviations that may be related to adverse events caused by the study treatment.
At the end of the scan, for those participants who received an a-line, an experienced nurse
practitioner or MD will remove the catheter. These subjects will be kept under observation for 30
minutes.
The total duration of each scanning visit will be up to 6 hours (~45min for preparation, ~30min
for a-line placement, if applicable, ~120 min for scanning procedures and 30 minutes (up to 60
minutes based on clinical opinion of NP) for filling out questionnaires and observation, plus an
additional ~1.5hr to perform pregnancy test in women of childbearing age). In case of equipment
failure (e.g., failure in radiosynthesis) delays of > 2 hours may be possible. In this case, we will
ask the participant if he or she feels comfortable with staying longer than anticipated, or will
prefer reschedule to another date.
Depending on the patients’ level of discomfort and time constraints, we may occasionally
shorten and simplify the scan visits. For instance, if the participant cannot remain for a full 6
hour scan visit, it will be acceptable to forego the placement of the arterial line. Eliminating this
procedure will save the time needed for the placement and the 30 minutes of observation needed
after the removal of the a-line (from these scans we will derive metrics that do not depend on
arterial sampling, such as SUVR). Additionally, if the participant would feel too uncomfortable
to lay down in the scanner for the full ~2:00 hours of scanning, we may administer the
radioligand in the injection room and then scan the participant between 45 and 90 minutes post-
injection.
We will follow up with all subjects by phone 24-48 hours following the imaging visit to monitor
for adverse events that may be related to radioligand administration and/or the initiation of study
treatment.
The imaging visit, including all the procedures described above, will be repeated a second time
after either a 2-week trial of minocycline or placebo (cLBP).
Randomization
Following the behavioral visit, sLBP subjects will be randomized to either the minocycline or
placebo group. The sLBP and cLBP subjects, will be randomized in a 1:1 ratio to receive either:
placebo (lactose powder), or minocycline 100mg once daily for 2 weeks. Randomization will be
performed by assigning each subject a randomization number via a computerized random
number generator. However, the Clinical Trials Pharmacy will maintain the specific subjects’
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treatment assignments (minocycline or placebo) for later identification. Patients and study staff
will be blinded to minocycline or placebo assignment.
Intervention arms
We will follow the same dosage and administration protocol used by Vanelderen et al to
demonstrate a statistically significant reduction in pain in patients with subacute lumbar
radiculopathy (N=17)39. Specifically, patients will be asked to take the study medication in the
morning with a glass of water 1h before or 1h after breakfast, to prevent interference of food
with gastrointestinal absorption of the drug37. Continuation of medication (e.g., NSAIDS) will be
permitted on the condition that patients will be on a stable dose for at least 1 month before the
baseline MR-PET scan. Because minocycline is known to reduce the effectiveness of oral
contraceptives, all subjects taking oral contraceptives will be counseled to use alternative forms
of birth control while taking the study medication.
The Jackson Compounding Center at Massachusetts General Hospital will prepare the
minocycline and placebo, encapsulated in identical opaque capsules. Minocycline and placebo
will be stored at controlled room temperature between 59-86 °F in a container that is kept tightly
closed and stored out of direct sunlight. Both the minocycline and placebo will have 25 mg of
riboflavin (vitamin B2) added to them for the purposes of tracking treatment compliance.
Riboflavin acts as a tracer and will allow us to do urine testing using a UV light to ensure that
subjects are taking the medication as instructed. Each container will be labeled with a unique
number that will be recorded by study staff at the time of administration. As soon as possible
after the 2-week minocycline or placebo period, patients will be re-scanned and/or re-evaluated
clinically to evaluate the hypothesis that minocycline reduces glial activation and pain
symptoms.
During the drug trial period, subjects will also be sent a daily survey via email (administered
through StudyTrax) to assess the treatment effect of the medication on their pain. The surveys
will also include contact information for the study physician in case they have any concerns
about the medication. If subjects do not have email access, they will be able to complete the
surveys over the phone.
Following the completion of the drug trial period, participants will be asked to complete a brief
questionnaire assessing their experience of the study medication.
Following the drug trial period, sLBP subjects will be sent a weekly survey via email
(administered through StudyTrax) to assess the progression of their pain. The surveys will also
inquire about pain management interventions used in the past week so that these can be tracked
throughout study enrollment and the effect on pain outcomes can be assessed. They will
complete these weekly surveys until their 6-month follow-up visit. Again, if subjects do not have
email access, they will be given the opportunity to complete the surveys over the phone.
Subjects will be paid by check at the completion of the study for their participation.
Payments will be as follows:
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-
$75 for the initial behavioral session (Visit 1)
-
$2 per daily baseline survey
-
$2 per daily survey for all treatment arms plus a $25 bonus for completing at least 12 of
the surveys
-
$5 per weekly survey for sLBP patients $25 bonus for completing at least 10 of the
surveys
-
$200 for each MR-PET scanning visit
-
$100 for each follow-up behavioral session
-
$50 for each arterial line placement
-
$25 for each blood test to exclude pregnancy (if the subject is female of childbearing age)
Participants will be able to earn up to an additional $17-$22 during the Monetary Incentive
Delay task.
If during the imaging visit(s) we cannot inject the subject with the radioligand (e.g., due to a
failure in radiosynthesis, or to issues with the scanner) and we HAVE NOT yet placed the
arterial line, he/she will receive $50. If we cannot inject the subject with the radioligand, and we
HAVE already placed the arterial line, he/she will receive $100.
If the subject will need to stop the scan early for any reason, he/she will still receive $50 for
his/her time. Additionally, parking fees will be covered as needed.
If a cost is incurred by the subject for obtaining medical records to confirm the diagnosis of low
back pain, we will reimburse the subject for this expense.
If subjects have difficulties traveling to our facility, we may offer travel reimbursement for their
cab or Uber fare up to $100.
If subjects are eligible to scanned but have difficulties with travel (i.e. out-of-state), we may offer
them 1 night’s stay at a hotel not exceeding $200.
Individuals will be compensated $25 for participation in the “Post-Lockdown Impact Survey” if
they were scanned prior to 7/1/2021. Participants scanned after this date will complete this
optional survey as part of the questionnaire set included in the MRI-PET visit for no additional
compensation.
7.
Benefits
It is unlikely that individual subjects will benefit from taking part in this study. While this study
is powered to possibly observe a statistically significant reduction in pain due to minocycline, it
is unclear whether the effect will be clinically meaningful. However, findings from these studies
will help advance our understanding of the pathophysiology of pain disorders. In particular, this
project will assess the role of microglia in the establishment and/or maintenance of chronic pain.
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As such, we envision that in the future the information obtained from the proposed research will
enhance the diagnosis and management of a variety of chronic pain conditions.
8.
Risks and Discomforts
All subjects will undergo a telephone or email screening to attempt to distinguish potential
subjects from those not meeting eligibility criteria. Likely candidates will undergo a
characterization and training session, which will include a clinical screening procedure. This
procedure will involve answering questions about subjects’ medical history recording of medical
history review and answering questions about their medical situation including liver disease,
kidney disease, blood disorders, heart disease, alcohol and opioid use, high blood pressure,
asthma and other respiratory disorders.
Subjects will be instructed to complete the questionnaires to the best of their ability, but will
have the option to leave any question(s) blank. In the unlikely event that evidence of physical or
psychological disorder is found, with the individual's permission, the information will be shared
with his or her primary care physician who can direct care as needed.
The U.S. Food and Drug Administration (FDA) recently gave the first regulatory clearance of a
hybrid PET/MRI scanner in the U.S. Additionally, FDA considers investigations of MRI
software and hardware operating within FDA specific parameters as non-significant risk device
studies. All studies will adhere to these FDA approved safety levels for the Siemens system.
These safety parameters include static magnetic field, time varying magnetic fields (dB/dt),
specific absorption rate (SAR), and acoustic noise levels. Subjects will be informed about
minimal risks of routine high magnetic field and non-ionizing RF radiation involved in MR
imaging.
Subjects will also be informed about the PET procedure and the minor risks associated with
exposure to radiation. Subjects will also be informed about small space within the magnet and
noises made by switching gradients. Subjects will be informed that if they feel uncomfortable
with the study, they can choose to terminate the study at any time. They will be informed that
their refusal to participate in the study or choosing to terminate it at some point will have no
effect on care and treatment received by them at MGH now or in future. The subjects will be
informed that their personal information will be protected as per the HIPAA guidelines.
An intravenous catheter will be placed for this study. The subject will feel a slight pinprick,
similar to a bee sting, and may feel some discomfort and have some bruising or bleeding at the
site where the needle goes in. Depending on the length of time the catheter is in place, a bruise
may last for a day or so. Rarely an infection may occur at this site. If infection does occur, it will
be treated. Also, an intra-arterial catheter will be placed by an individual with anesthesia
training(i.e., board-certified anesthesiologist, fully licensed anesthesia resident, or a certified
registered nurse anesthetist), on the arm opposite to the radio-ligand injection line, for blood
draws during the PET study. Local infection, swelling, and redness could occur at the sites of
line placement, as well as temporary loss of pulse at the wrist. This area may have a bruise or
feel uncomfortable for 2-3 days after the catheter is removed. The risks associated with having
blood drawn include: bruising, local discomfort, or infection at the site of the needle puncture.
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Rarely an infection may occur at this site, and if an infection does occur, it will be treated.
Inserting an arterial line (A-line) can hurt more than having a regular IV or having blood drawn
with a needle. We will place the A-line under local anesthesia (i.e., lidocaine), which may cause
an allergic reaction. Even if we numb the wrist area first, the insertion may still hurt. Once the A-
line is in place, it usually does not hurt.
The subject may experience pain, bleeding, swelling or redness at the wrist, short loss of pulse at
the wrist if blood flow in the artery is briefly stopped, damage to the artery wall or nearby
nerves, or catheter breaking or falling out. There have been reports of decreased blood flow to
the hand, which resulted in the need for surgery. This is very rare and has not been reported
when catheters have been in place for only a few hours for research. A subject who will not pass
the modified Allen’s test during the screening visit will not be considered eligible for the
imaging visit, including A-line placement. Additionally, the insertion or removal of the A-line
might cause temporary dizziness, nausea or fainting. After the anesthesiologist, anesthesia
resident, certified nurse anesthetist or RN removes the catheter and has held pressure for several
minutes, we'll ask the subject to stay for 30 minutes (up to 60 minutes based on clinical opinion
of NP) so we can monitor him/her in order to assess the occurrence of any adverse event. Dr.
Loggia will file a report on Insight within the timeframe stipulated by the IRB (5 working days/7
days) should any adverse event occur. The subject may have a bruise or feel tenderness for 2-3
days around the area where the catheter was placed. We will instruct the subject to avoid lifting
anything heavier than a small bag of flour for a day. We will instruct the subject to call us if
bleeding occurs after the subject leaves (rare), and/or if the wrist area is painful or red or
swollen. About 24 hours after the beginning of the imaging procedures, we will give the subject
a phone call to determine whether he or she is experiencing study related issues.
The radiation exposure in this study will be small and there is no evidence that it represents a
major health risk. If subjects have participated in other research studies in the past 12 months
that have involved radiation exposure, they will be asked to inform the investigators or study
staff (by writing initials on the consent form verifying that they have not been exposed to other
radiation in the past 12 months). If it is determined that their prior radiation exposure exceeds
our current guidelines, they may not be allowed to participate in this study.
We will use [11C]PBR28 produced by the cyclotron/radiochemistry/radiopharmacy facility at the
A. A. Martinos Center for Biomedical Imaging. The Martinos Center has studied several
hundreds of people with this radioligand and have had no clinically detectable effects or side
effects.
Given the use of [11C]PBR28 in a small clinical trial, we are in the process of requesting an IND
from the FDA.
The IV injection will be administered by a licensed nuclear medicine technologist. Should there
be an adverse event, Dr. Loggia will be responsible for communicating with the IRB within the
stipulated time frame.
Imaging will be stopped should any untoward reaction be observed during the imaging session or
if the participant so requests for whatever reason. Some subjects find it unpleasant or feel
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anxious when confined in the enclosed space of the scanner. If this happens, the study will be
aborted. Patients will be required to use earplugs to decrease the noise perceived while in the
scanner.
Minocycline is an FDA approved antibiotic used to treat infections. Common side effects include
dizziness (9 in 100 people), drowsiness (2 in 100 people), headache (23 in 100 people). Less
common side effects (1 in 1,000 to 1 in 10,000 people) include sun sensitivity (photosensitivity).
Uncommon side effects (less than 1 in 10,000 people) include the development of drug resistant
infections. Additionally, side effects with unreported frequency include Clostridium difficile
colitis (severe diarrhea caused by infection), gastrointestinal disturbance, diarrhea, indigestion,
loss of appetite, nausea, vomiting, lightheadedness, sore mouth, throat, or tongue, tooth
discoloration. Some of the side effects, especially diarrhea, may continue even after minocycline
is no longer being taken. Subjects will be informed of all these potential adverse effects, and will
be asked to immediately contact the Dr. Zhang (the main study MD investigator) if they
experience any of them.
Riboflavin is a commonly consumed supplement, and is often use as a tracer to monitor
compliance in clinical studies75-80. There is no evidence for riboflavin toxicity produced by
doses comparable to those used in the present study. After administering 400mg of riboflavin
daily (16 times the daily dose used in this study) for three months (i.e., a treatment period 6 times
longer than in this study), no short term side effects were reported 81.
Minimal risks associated with completing questionnaires are subject fatigue and the possibility of
minor psychological distress associated with answering sensitive questions regarding
psychological functioning. Minimal discomfort may occur due to the time and effort related to
completing the Monetary Incentive Delay and Probabilistic Reward Tasks.
As detailed, the investigators are quite careful regarding the protection of confidentiality, and
multiple procedures are in place to reduce the likelihood of a breach of confidentiality. However,
there is a small risk that information about subjects could become known to people outside of
this study, and this risk is identified in the informed consent form.
The key investigators will meet quarterly to discuss any potential adverse event and side effects.
We will involve the MGH Human Research Committee and Radiation Safety Committee if any
additional potential risks arise. Adverse events and unanticipated problems involving risks to
subjects or others will be reported to the PHRC in accordance with PHRC adverse event and
unanticipated problems reporting guidelines, as well as FDA when appropriate.
In this study, we aim to administer only tolerable thermal or electrical pain stimuli. However, if a
participant feels that the stimuli has become intolerable, the participant can stop the stimulation
at any time by letting the experimenters know. There is a very small chance that the heating
device might produce a minor burn, but the risks associated with relatively small amount of heat
applied to the skin (maximum of 50°C, for very short periods of time) are very low. Our group82-
88 and many others around the world have used similar or identical heat pain testing procedures
in a number of previous studies with healthy adults and patients with chronic pain. No serious
side effects were ever reported.
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9.
Statistical Analysis
MR-PET scanning will be performed at 3 Tesla, using Siemens TIM Trio whole-body MRI with
head PET camera, and/or Siemens Verio whole-body MRI, whole-body PET camera (Biograph
mMR).
PET
During each visit, [11C]PBR28 (up to 15 mCi, corresponding to ~3.7mSv) will be injected
intravenously with a slow bolus over a 30-60s period67. This dose is compatible with a
longitudinal study, because the total radiation of maximum ~7.4mSv received by the subjects
participating in two scans will be significantly less than the maximum allowed annual whole-
body dose set by the U.S. Food and Drug Administration at 5 REM, i.e., 50mSv). The catheter
will be flushed post-injection with 0.9% saline solution. Dynamic data will be collected over
~120 minutes in list mode, and framed post-collection. At various times during the PET
acquisition we will perform arterial blood sampling as described above, if the participant has
consented to receive an arterial line. Regional uptake of the tracer will be estimated as SUV,
SUVR, Vt and/or DVR.
MRI
MRI data will be acquired simultaneously to the PET data, and may include some or all of these
standard sequences: BOLD fMRI (for functional connectivity analyses, to evaluate brain
responses to the reward task, and/or to estimate motion parameters), Diffusion-Spectrum or
Diffusion-Tensor Imaging volumes (DSI) (to perform tractography analyses), Arterial Spin
Labeling (to estimate resting state regional cerebral blood flood); Chemical shift imaging (to
estimate brain metabolites); a high resolution structural volume (for anatomical reference,
cortical reconstruction, volumetric segmentation, and attenuation correction); in addition to
various T1 and T2 weighted structural volumes.
Behavioral measures
Before, during and after the scans, subjects may be asked (either verbally, or using a button box
connected to a computer) to express various behavioral ratings, including pain intensity,
unpleasantness, and anxiety.
All fMRI data will be stored on hard drive and storage clusters. Behavioral data will be recorded
and stored in StudyTrax in preparation for statistical analyses. StudyTrax is approved by Partners
Research Information Science and Computing and is compliant with 21 CFR Part 11.
In order to address the first aim (‘Assess spatial extent and and somatotopic organization of
glial activation in chronic LBP’), we will compare [11C]PBR28 PET brain and spinal cord
maps between radicular cLBP patients, axial cLBP patients and healthy volunteers. We will
perform an unpaired comparison of the imaging data between all 3 groups, including age, sex
and TSPO genotype (which predicts binding affinity52) as covariates of no interest. Additional,
secondary regression analyses will be performed in order to evaluate the association between
imaging and behavioral data (e.g., questionnaire scores, pain duration, etc). The effect of
painkillers (e.g., NSAIDs) on the PET signal will be evaluated by performing subanalyses on
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patients not taking any medication, or by adding use of medication as a covariate of no interest,
depending on the profile of drug usage observed in the samples we will have recruited.
These analyses will be performed voxelwise for the brain data, using methods similar or identical
to those we have previously used36, as well for spinal cord data using methods developed by Dr.
Cohen-Adad68. In addition to these voxelwise analyses, for the spinal cord we will perform
region-of-interest (ROI) analyses focused on the spinal cord segments contained in the T11-L1
vertebral levels (as these contain the lower lumbar/upper sacral spinal cord segments). The ROI
data, as well as demographic and behavioral data (age, sex, polymorphism, axial vs radicular
symptoms, and the questionnaires) will be compared across groups with a one-way analysis of
variance (ANOVA) followed by Dunnett’s post-hoc pairwise tests. In addition, we will run
regression analyses to evaluate the association between the [11C]PBR28 data, and
sensory/affective pain ratings as well as negative affect scores and blood data (e.g., levels of IL-6
and TNF-alpha).
Using ANOVAs we will compare ratings of thermal stimuli across groups to determine whether
they differ in terms of pain sensitivity. We will also evaluate the association between imaging
metrics (e.g., PET signal) and pain sensitivity to test the ancillary hypothesis that higher pain
sensitivity is correlated with higher neuroinflammation.
For the second aim (‘Assess temporal evolution of glial activation in subacute LBP), we will
perform unpaired comparison between sLBP patients and cLBP patients, for both spinal cord and
brain. In addition, we will separate the sLBP subjects in 2 groups, based on their follow-up
clinical evaluation at 6 months post pain-onset: those who have healed, and those who have
transitioned to cLBP. We will then compare the imaging as well as behavioral data from the
baseline scans across these two subgroups, to assess whether imaging data can be used as
predictor of pain chronification. Comparisons of voxelwise, ROI and demographic/ behavioral
data will be performed as described above.
For the last aim (‘Assess the effect of minocycline on glial activation and pain, and the role
of minocycline as predictor of response to minocycline’), we will perform paired analyses in
cLBP receiving minocycline or placebo (pre vs post treatment) and test for a treatment*time
interaction. In addition, we will use regression analyses to assess the hypothesis that baseline
PET signal predicts changes in pain after minocycline treatment.
In addition to these main analyses done with the PET data, additional, exploratory analyses will
be performed on the MRI data (BOLD resting state, diffusion, spectroscopy, etc) collected
simultaneously to the PET data.
All voxelwise analyses will be conducted using the FSL suite69 for the brain, and using the
Spinal Cord Toolbox68 for the spinal cord. Group comparisons maps will be thresholded using
threshold-free cluster enhancement70, and a corrected threshold of p=0.05. All behavioral,
demographic and ROI data will be analyzed using Statistica 10.0 (StatSoft Inc., USA), and an
alpha level of 0.05.
Consideration of sex as a biological variable
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In addition to the aforementioned analyses, the effect of sex will be evaluated using ANOVAs
for all aims, because animal research suggests the presence of a possible sexual dimorphism in a)
the role of glia in pain (as pain hypersensitivity may be microglial-dependent only in males71)
and in b) the effects of minocycline (as this drug may decrease the expression of glial activation
markers and increase acute morphine analgesia only in males)72. The effect of menstrual cycle
status will also be evaluated by comparing women in early follicular (day 2-7 after onset of
menses) and midluteal (day 20-25 after onset of menses), based on self-report73.
Functional MRI data from the Monetary Incentive Delay (MID) task as well as resting state
scans, MRS, PCASL, etc will be analyzed with established analytic procedures (regression
analysis, General Linear Model) using commonly used imaging software (FSL, FreeSurfer,
LCModel, etc).
Effect of coronavirus on neuroinflammation. Finally, in addition to the aforementioned analyses,
the effect of prior exposure to coronavirus (as detected by the presence of antibodies to SARS-
CoV-2 ) will be evaluated in both ROI and voxelwise analyses, in exploratory analyses. While
we will be explicitly excluding for participants who had been diagnosed with COVID-19 in the
previous 3 months with neurological symptoms that required hospitalization (to avoid that the
acute/subacute effects of the disorders might confound our main analyses on the role of
neuroinflammation in chronic back pain patients), identifying participants who are positive to the
antibodies might allow us to test the exploratory hypothesis that prior exposure to the
coronavirus can lead to neuroinflammation even without having experienced overt acute
COVID-19 symptoms.
In order to power the study, we computed the sample size required for a mixed between subject
(Treatment Group: Minocycline/Placebo) and within subject (Time: Pretest/Posttest) repeated
measures ANOVA design using the pain ratings on a 0-100 numerical ratings scale as the
dependent variable. Alpha was set at 0.05 (2 tailed test). Based on data from a previously
studied cohort of cLBP36, we assumed a mean rating of 50 and a standard deviation of 20 before
treatment. In addition, we assumed a test-retest correlation of r=0.65, based on a large (n=200)
test-retest study74. In terms of effect size, we assumed a reduction of 15 points in the minocycline
group (in the Vanelderen trial a reduction of ~1.5 was observed on a 0-10 scale)39, and a
negligible (1 point) reduction in the placebo group. For these specifications and 80% power to
detect the interaction of Treatment Group X Time, the total sample size required for the study
was computed to be 48 (i.e., 24 per group).
In addition, we powered our study to be able to detect differences between patients and controls.
This analysis was performed using the fMRIpower software package (fmripower.org). This
method, which can be used for any brain imaging data including PET, estimates power for
detecting significant effects within specific regions of interest, with the assumption that the
planned studies will have the same number of runs per subject, runs of the same length, and data
analysis with a comparable model. The effect sizes have been expressed in standard deviation
(SD) units, which is analogous to the Cohen’s D measure. These power calculations are based on
our previous brain [11C]PBR28 study in chronic low back pain patients4, and employed the same
thalamic region of interest (ROI) used from that study (the thalamic labels from the Harvard
Oxford atlas), with a p-value threshold of 0.05 for a 1-sided hypothesis test. With 23 patient-
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control pairs, we will have > 90% power to detect an effect of size of 0.64 SD in the left
thalamus, and of 0.62 SD in the right thalamus. Thus, with the proposed sample size we will be
able to also detect a group difference in [11C]PBR28 signal.
In addition, we will explore whether environmental exposure may be a potential confound to our
results. To do so, we will evaluate – in ancillary/exploratory analyses – whether
neuroinflammation might be influenced by environmental and other factors, such as pollution
and proximity to roads, that are thought to induce neuroimmune activation. We will estimate
environmental exposure by linking residential address at time of scan with pollution levels (e.g.,
PM2.5, ozone levels, etc.) extracted from publicly available (i.e., meteorological) records, and use
this information to run regression analyses against brain and clinical/behavioral data.
We will also perform kinetic modeling analyses of the PET data, morphometric analyses of MRI
data, and/or implement machine learning algorithms to create objective classifiers that can
reliably distinguish between healthy volunteers and patients with chronic pain. Using our MRI
data, we would like to evaluate potential anatomo-functional alterations, and their association
with neuroinflammation, in patients with chronic pain.
10.
Monitoring and Quality Assurance
The proposed study will be monitored for safety, with monthly staff meetings reviewing adverse
events and treatment outcomes and directly reporting any adverse events. The PI will also
routinely monitor and assure the validity and integrity of collected data and adherence to the
IRB-approved protocol. The trained staff members who carry out the procedures will also
carefully monitor the study throughout its duration. The team will evaluate the progress of the
study, verify that the rights and well-being of the subjects are protected, verify that the reported
study data are accurate, complete and verifiable from source documents, and the conduct of the
study is in compliance with the approved protocol and amendments. Outcome monitoring and
adverse events will all be reported through appropriate channels of the Human Studies
Committee as well to the FDA when appropriate.
The Siemens MR-PET scanners have a built in self-monitoring system that automatically shuts off
if parameters exceed safe levels. For backup protection NMR technicians constantly monitor the
subjects’ physiological signs and the quality of the raw data.
Quality assurance of the scanner’s performance is obtained by a daily quality assurance protocol.
More extensive quality assurance protocols are performed monthly under the commercial service
contract with Siemens Medical Systems. The daily quality assurance protocol consists of an
image Signal-to-Noise measurement in a phantom and a stability run which checks the image-to-
image variation in image intensity over 600 images using a standard echoplanar imaging
sequence with a head-sized phantom. The images are analyzed by the technologist to provide
data on SNR (as an absolute, unitless number) and stability expressed as the peak-to-peak
variation in the mean of a 15x15 pixel region of interest (ROI) in the center of the phantom
expressed as a percentage of the mean of the ROI. Runs are performed at each of 3 TR values
(300ms, 800ms, 1300ms). The time course of the means is also reviewed to check for
periodicities (the TR values are chosen so as not to be multiples of one another). If the peak-to-
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peak variation is greater than 0.5% of the mean value, the Siemens Medical System service
engineer is called. In addition to these daily quality assurance tests, the Siemens Medical
System service engineer performs quality assurance tests once a month. These tests include a
SNR test, a small sample stability test, a gradient stability test, a gradient eddy current test, a
shim test, an image uniformity test, and an RF stability test.
11.
Privacy and Confidentiality
☒Study procedures will be conducted in a private setting
☒Only data and/or specimens necessary for the conduct of the study will be collected
☒Data collected (paper and/or electronic) will be maintained in a secure location with appropriate
protections such as password protection, encryption, physical security measures (locked
files/areas)
☒Specimens collected will be maintained in a secure location with appropriate protections (e.g.
locked storage spaces, laboratory areas)
☒Data and specimens will only be shared with individuals who are members of the IRB-approved
research team or approved for sharing as described in this IRB protocol
☒Data and/or specimens requiring transportation from one location or electronic space to another
will be transported only in a secure manner (e.g. encrypted files, password protection, using
chain-of-custody procedures, etc.)
☒All electronic communication with participants will comply with Mass General Brigham secure
communication policies
☒Identifiers will be coded or removed as soon as feasible and access to files linking identifiers with
coded data or specimens will be limited to the minimal necessary members of the research team
required to conduct the research
☒All staff are trained on and will follow the Mass General Brigham policies and procedures for
maintaining appropriate confidentiality of research data and specimens
☒The PI will ensure that all staff implement and follow any Research Information Service Office
(RISO) requirements for this research
☐Additional privacy and/or confidentiality protections
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Mass General Brigham Institutional Review Board
Intervention/Interaction Detailed Protocol
APPENDIX A
Data Monitoring Committee / Data and Safety Monitoring Board
Appendix
•
To be completed for studies monitored by Data Monitoring Committee (DMC) or Data and Safety
Monitoring Board (DSMB) if a full DMC/DSMB charter is not available at the time of initial IRB
review.
•
DMC/DSMB Charter and/or Roster can be submitted to the IRB later via Amendment, though these
are not required.
A Data Monitoring Committee (DMC) or Data and Safety Monitoring Board (DSMB) will be convened
for safety monitoring of this research study. The following characteristics describe the DMC/DSMB
convened for this study (Check all that apply):
☐The DMC/DSMB is independent from the study team and study sponsor.
☐A process has been implemented to ensure absence of conflicts of interest by DMC/DSMB
members.
☐The DMC/DSMB has the authority to intervene on study progress in the event of safety concerns,
e.g., to suspend or terminate a study if new safety concerns have been identified or need to be
investigated.
☐Describe number and types of (i.e., qualifications of) members:
Click or tap here to enter text.
☐Describe planned frequency of meetings:
Click or tap here to enter text.
☐DMC/DSMB reports with no findings (i.e., “continue without modifications”) will be submitted
to the IRB at the time of Continuing Review.
☐DMC/DSMB reports with findings/modifications required will be submitted promptly (within 5
business days/7 calendar days of becoming aware) to the IRB as an Other Event.
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