18F and 11C Chemistry ChallengesProf. Peter J. H. Scott

Associate Professor of RadiologyDirector of PET Radiochemistry

•Owner of SYNFast Consulting, LLC

•Consulting(JUAMA Medico)

•Royalties and Honoraria(Zevacor Molecular, Thieme, John Wiley and Sons)

•Research funding(NIH, Alzheimer’s Association, DOE, the University ofMichigan, Avid Radiopharmaceuticals / Eli Lilly, MolecularImaging Research, Bristol-Myers Squibb, Merck, ThresholdPharmaceuticals, Adeptio, GE Healthcare)

Disclosures

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New PET Center opened in 2006 and expanded in 2010

• GE PETTrace and Ionetix Cyclotrons

• 2 x Gallium-68 Generators

• 8 full-size hot-cells, 4 mini-cells and 1 dispensing hot-cell

• 9 GE TRACERlab & FASTLab 2 F18/C11 Synthesis Modules(2 x FL2, 2 x FXFN, 1 x FXNPro, 2 x FXC-Pro, 1 x FXM)

• Scintomics Ga68 Synthesis Module

• Eckert and Ziegler Modular Lab Dispenser

• 2 x Full QC laboratories

The University of Michigan PET Center

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Clinical NM Suite

• 3 clinical Siemens Biograph PET-CT scanners

• Several clinical SPECT-CT scanners

Pre-clinical Imaging (rodents and 2 dedicated rhesus monkeys)

• PET Center: Concorde rodent (PET and SPECT-CT) and non-human primate (PET) scanners (F18, C11 and Ga68). Upgrade to MR Solutions NHP PET in progress

• CMI (Brian Ross): Siemens Inveon (PET-CT) and MR solutions (PET-MRI) rodent scanners (F18, Ga68), as well as MRI, Bioluminescence, NFIR etc.

The University of Michigan PET Center

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UM “First-in-Man”Translational Experience

[131I]NP-59* 19-noriodocholesterol steroid hormone synthesis[131I]/[123I]MIBG* iobenguanidine peripheral NET[11C]SCOP* scopolamine muscarinic cholinergic receptors[11C]TRB tropanylbenzilate muscarinic cholinergic receptors[11C]NMPB N-methylpiperidylbenzilate muscarinic cholinergic receptors[11C]PK11195* “peripheral” BZ receptor (TSPO)[18F]GBR12909 dopamine neuronal transporter [11C]TBZ tetrabenazine vesicular monoamine transporter-2[11C]MTBZ methoxytetrabenazine vesicular monoamine transporter-2[11C]DTBZ dihydrotetrabenazine vesicular monoamine transporter-2[11C]PMP N-Methylpiperidinylpropionate acetylcholinesterase substrate[11C]BMP N-Methylpiperidinylbutyrate butyrylcholinesterase substrate[11C]HED hydroxyephedrine peripheral NET[11C]EPI epinephrine peripheral NET[11C]PHE phenylephrine peripheral NET [18F]AV-19** CNS Ab-amyloid binding[18F]AV-133** fluoropropyl dihydrotetrabenazine vesicular monoamine transporter-2[123I]IBVM* iodobenzovesamicol vesicular acetylcholine transporter[18F]MHPG/PHPG guanidine derivatives peripheral NET[18F]FEOBV ** fluoroethylbenzovesamicol vesicular acetylcholine transporter[11C]Sarcosine * oncology[18F]NML*** N-methyl lansoprazole tau

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* IND; ** eIND; *** with Positronpharma, Chile

Radiotracers Synthesized for Routine Use

CARBON-11

•[11C]Acetate (TCA Cycle – Cardiac, Oncology)

•[11C]Butanol (Blood flow)

•[11C]Carfentanil (Opioid)

•[11C]Choline (Oncology)

•[11C]DASB (SERT)

•[11C]DTBZ (VMAT2)

•[11C]FMZ (BZD)

•[11C]HED (Adrenergic)

•[11C]Methionine (Oncology)

•[11C]Palmitate (Cardiac)

•[11C]PBR28 (Neuro, Cardiac and Oncology)

•[11C]PiB (Amyloid)

•[11C]PMP (Acetylcholinesterase)

•[11C]Raclopride (Dopamine)

•[11C]Sarcosine (Prostate cancer)

FLUORINE-18• [18F]FDG• [18F]NaF• [18F]FLT (Cell proliferation)• [18F]FAZA (Hypoxia)• [18F]Flubatine (NAChRs)• [18F]Fluorocholine (Prostate cancer)• [18F]FEOBV (VAChT)• [18F]MPPF (5HT-1A)• [18F]ASEM (alpha 7)• [18F]N-Methyl Lansoprazole (tau)• [18F]AV1451 (tau)

NITROGEN-13• [13N]NH3 (cardiac)

RUBIDIUM-82• [82Rb]RbCl2 (cardiac)

GALLIUM-68• [68Ga]PSMA-11 (prostate cancer)• [68Ga]NETSPOT (NET)

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Translation of a Radiotracer: Overview

1. Regulatory Considerations

2. Chemistry Considerations

3. Quality Considerations

4. Questions / Discussion

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1. Regulatory Considerations

First things first… Will you operate under RDRC, IND or (A)NDA?

• Depends on what you want to do

• Choice has implications for regulatory filings and how tracers need to be manufactured (RDRC/IND: USP823, (A)NDA: 21CFR212)

• We consider the RDRC mechanism first

Guidance for Clinical Investigators, Sponsors, and

IRBs

Investigational New Drug Applications (INDs) —

Determining Whether Human Research Studies Can Be

Conducted Without an IND

U.S. Department of Health and Human Services Food and Drug Administration

Center for Drug Evaluation and Research (CDER) Center for Biologics Evaluation and Research (CBER)

Center for Food Safety and Applied Nutrition (CFSAN)

September 2013 Clinical/Medical

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Which Regulatory Pathway?

1. Has it been in man before?

2. Will you conduct basic science with it?

•Yes – Yes è RDRC Application (approval by local RDRC)

•Yes – No, No – Yes or No – No è IND Application and possibly subsequent (A)NDA (approval by FDA)

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RDRCThe regulations list three main requirementsfor human subject research that may beconducted under an RDRC:

• The research must be basic science.

• The dose to be administered must beknown not to cause any clinicallydetectable pharmacological effect inhumans (21 CFR 361.1(b)(2)).

• The total amount of radiation to beadministered as part of the study must bethe smallest radiation dose practical toperform the study without jeopardizing thebenefits of the study, and must be withinspecified limits (21 CFR 361.1(b)(3)).

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Guidance for Industry and Researchers

The Radioactive Drug Research Committee: Human Research Without An Investigational New Drug

Application

Additional copies are available from: Office of Training and Communication

Division of Drug Information, WO 51, Room 2201 Center for Drug Evaluation and Research

Food and Drug Administration 10903 New Hampshire Ave.

Silver Spring, MD 20993-0002 Phone: 301-796-3400; Fax: 301-847-8714

druginfo@fda.hhs.gov http://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/default.htm

and/or

Office of Communication, Outreach, and Development Center for Biologics Evaluation and Research

Food and Drug Administration 1401 Rockville Pike, Suite 200N, Rockville, MD 20852-1448

http://www.fda.gov/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/default.htm (Tel) 800-835-4709 or 301-827-2000

U.S. Department of Health and Human Services Food and Drug Administration

Center for Drug Evaluation and Research Center for Biologics Evaluation and Research

August 2010 Clinical/Medical

Guidance Investigational New Drug Applications

for Positron Emission Tomography (PET) Drugs

GUIDANCE

U.S. Department of Health and Human Services Food and Drug Administration

Center for Drug Evaluation and Research (CDER)

December 2012 Clinical/Medical

INDAn IND is required if:• This is a first-in-man study of the molecule.

Note: RDRC may still be appropriate if a non-radioactive version of your molecule has been safely used in man previously (e.g. as a pharmaceutical, endogenous compound etc.) at doses (typically µg/kg) above your planned dose

• You plan on following the drug discovery pathway for the radiopharmaceutical (Ph. I à Ph. 2 à Ph. 3 à NDA/Market)

• You want to use the radiopharmaceutical to make clinical decisions (e.g. where should I target radiotherapy, what drug should this patient be treated with)

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(A)NDA• An (Abbreviated) New Drug Application (A)NDA

contains data which when submitted to FDA's Center for Drug Evaluation and Research, provides for the review and ultimate approval of a (generic) drug product.

• Once approved, an applicant may manufacture and market the (generic) drug product to the American public.

• FDA product approval does not guarantee reimbursement; reimbursement may be limited to only FDA-approved indications, and only occurs after CMS approval. However, CMS’ determinations are not uniform throughout the country.

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2. Chemistry Considerations

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Decide which regulations you’re operating under

RDRC/INDà USP823;(A)NDAà 21CFR212

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Both USP823 and 21CFR 212 are very similar today

1. General Provisions2. Personnel and Resources3. Quality Assurance4. Facilities and Equipment5. Control of Components, Containers, and Closures6. Production and Process Controls7. Laboratory Controls8. Finished Drug Product Controls and Acceptance9. Packaging and Labeling10. Distribution11. Complaint Handling12. Records

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Develop the Synthesis

Use (or adapt) literature methods as a starting point for known radiotracersor develop de novo synthesis of new tracers for first-in-man studies.Reactions should be:

• Quick (typically < 10 mins but depends on half-life);

• High radiochemical yield (i.e. ~8-16 mCi injected, enough to get animage!);

• High specific activity (so that mass injection limits are not exceeded)

• Easy to purify (HPLC or Solid-Phase Extraction [SPE]);

• Provide stable products as sterile isotonic solutions suitable for IVadministration;

• Ideally fully automated, and conducted in compliance with USP <823> or21CFR212.

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Qualify the Synthesis

• Once the synthesis is set in stone, and no more changes will be madeto the method, process verification runs need to be completed

• These consist of three back-to-back successful runs

• Products must pass all QC testing

• Stability tests should be conducted out to the proposed expiration time ofthe radiotracer, including visual inspection, pH and radiochemical identity /purity (TLC / HPLC)

• Runs should be reviewed by RDRC, or submitted to the FDA in the IND or(A)NDA

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3. Quality Control Considerations

Quality control needs to be rapid (≤20 min) and must quickly and reliably identify ifthe radiotracer dose is suitable to administer to a patient. Required tests are laid outin USP<823> and 21CFR212, and include:

• Visual Inspection• pH• Residual K-2.2.2 (F18, spot-test)• Radiochemical purity (TLC or HPLC)• Chemical purity (HPLC)• Residual solvent analysis (GC)• Radionuclidic identity (half-life)• Radionuclidic purity (annual, MCA)• Osmolality (annual)• Sterile filter integrity• Bacterial endotoxins• Sterility

QualityControlChallenges

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1. Residual Solvent Analysis

“Forresidualsolvents,thedrugproductshouldcontainnomoresolventthanallowedperICHQ3C.”

Elimination of class-2 residual solvents from radiosyntheses?

• As one aspect of Quality-by-Design, we wished to eliminate the risk of dosesfailing QC testing (and risk to patients from errors) because of contamination withresidual solvents used during radiotracer manufacturing (e.g. MeCN, DMF), byremoving such solvents from the manufacturing process and replacing them withsafer alternatives (water, EtOH, DMSO).

• USP<823> suggest that for syntheses employing Class III solvents ONLY (forcleaning, synthesis, HPLC, reformulation etc.), then residual solvent analysis canbe a periodic QC test (e.g. quarterly, annually etc.) simplifying workflow andthroughput.

• Therefore, we have been working on eliminating Class II solvents from oursyntheses – green radiochemistry

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1. Residual Solvent Analysis

• Carbon-11 and fluorine-18 radiochemistry can be conducted using ethanol as theonly organic solvent for module cleaning, synthesis, HPLC, and reformulation

• Residual solvent analysis conducted on annual PV runs, rather than every synthesis

CFN CHO DASB DTBZ FDG HED MET OMAR PBR28 PIB PMP RAC

Clean

Old

Acetone

Synth DMSO EtOH MEK DMF MeCN DMF Acetone DMSO MeCN 3-Pen DMF MEK

Purif PrOH EtOH MeCN EtOH MeCN/MeOH MeCN MeCN EtOH

Clean

Green EthanolSynth

Purif

Nucl.Med.Biol.2013;40:109;Appl.Radiat.Isot.2014;89:125;Chem.Commun.2015;14805.

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2. Volume

“Explainhowthefinalvolumeofthedrugproductisdetermined.Thefinalvolumeisthevolumeleft

inthedosevialafteranaliquotofsampleisremovedforQCtests.Beadvisedthatimprecisedeterminationofthefinalvolumecanresultinincorrectdeterminationoftheradioactivityconcentration,andthusresultinincorrect

‘strength’ofthedrugproduct.”

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2. Volume

• Historically, the fixed formulation programing of the automated synthesis moduledetermined the final product volume at end-of-synthesis (EOS). e.g. Sterile saline,USP (9.5 mL) and 200 proof EtOH, USP (0.5 mL) were measured with syringes,loaded into the synthesis module and combined during formulation to produce the 10mL dose.

• The radioactivity in the vial can then be assayed before or after removal of a 0.5 mLsample to conduct QC tests. Recording the dose volume and radioactivity at EOS inthis fashion was considered adequate, since it is for information only and does not getused to calculate patient doses.

• However we recognize that this practice is no longer in line with the current thinking ofthe FDA.

• To calculate the volume of the dose, weight or volume based methods can beemployed. The weight-based method involves weighing the dose vial and subtractingthe tare weight, while the volume-based approach involves measuring the radioactivityin a known volume of the dose drawn by calibrated mechanical pipette.

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3. Chemical Purity

“Thereleasecriteriashouldincludeatestforchemicalpurity.Werecommendthe%chemical

puritybecalculatedasyoudidwiththe%radiochemicalpurity,andsetthe%chemicalpurityreleasecriteriontobe>90%byUVarea.”

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Chemical Purity – Scenario 1

Minutes0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

mVolts

-400

-200

0

200

400

600

800

1000

mVolts

-400

-200

0

200

400

600

800

1000

Minutes0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

mVolts

0

5

10

15

20

25

30

35

40

mVolts

0

5

10

15

20

25

30

35

40

11.191

• In 2017 we frequently makevery high specific activityradiotracers

• Incaseswherenomassisdetected(i.e.≤LoD),whatisthechemicalpurity?

• 0%?Shouldwerejectthebatch?

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Chemical Purity – Scenario 2

Minutes0 1 2 3 4 5 6 7 8 9 10

mVolts

-4

-3

-2

-1

0

1

2

3

4

mVolts

-4

-3

-2

-1

0

1

2

3

4

3.133 5.733

Minutes0 1 2 3 4 5 6 7 8 9 10

mVolts

0

50

100

150

200

250

mVolts

0

50

100

150

200

250

0.5420.900

1.1251.3831.667 2.058

5.766

Dose1(160mCi)34%chemicalpurity

0.08µg/mLproduct,0.150µg/mLprecursor1mLinjected=0.0011µg/kgin70kgsubject

Minutes0 1 2 3 4 5 6 7 8 9 10

mVolts

-1.75

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0.25

mVolts

-1.75

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0.253.083

5.675

Minutes0 1 2 3 4 5 6 7 8 9 10

mVolts

0

50

100

150

200

250

300

mVolts

0

50

100

150

200

250

300

0.858 1.6672.042

5.700

Dose2(160mCi)52%chemicalpurity

0.162µg/mLproduct,0.148g/mLprecursor1mLinjected=0.0023µg/kgin70kgsubject

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Mass Injection Limits – What is the spirt of the regulations

• For RDRC studies, “the dose to be administered must beknown not to cause any clinically detectablepharmacological effect in humans”.

• Mass injections limits for radiotracers are therefore basedupon prior use of the radiotracer at your facility orelsewhere (RDRC), or from Pharm-Tox for new tracers.

• Amicrodose is defined as less than 1/100th of the dose of atest substance calculated (based on animal data) to yield apharmacologic effect (no observable adverse event level(NOAEL) of the test substance with a maximum dose of<100 micrograms)

ThoughtExperiment:I’mconsideringsynthesizingaseriesofnewPETradiotracersinmylab

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Green– OK; Yellow– Maybe,butwillneedverygoodspecificactivity;Red– No

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PEThasexquisitesensitivity… coldmassisnotanissuewiththetracerswearepreparing

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Proposed Alternative?

• % Chemical Purity is an arbitrary number that would lead to rejection of otherwise highquality usable PET drugs at great inconvenience (and expense) to PET Centers, physiciansand patients alike

• Possible alternative 1: do we need a chemical purity requirement at all? For all of thedoses we are preparing, most (>90%) of the time you can inject the entire vial withoutexceeding our mass injectable limits

• What about residual precursor and/or by-products? If we start with 500 µg of precursor,500/70 = 7 µg/kg in a 70 kg patient. For anything less toxic than arsenic, this is ok andyou could inject all of the precursor too and still be 100x than the NOAEL (assumingequivalent potency)!

• So, perhaps possible alternative 2: specify tracer and other impurity mass must be ≤XXµg/mL or YY µg/dose (either combined numbers or separate numbers), or have no masscriteria in radiochemistry and let the PET suite calculate it on a per study basis

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Summary

• Radiotracers can be used under RDRC, IND or (A)NDA

• Each regulatory mechanism has implications regarding how tracers are synthesized(USP<823>, 21CFR212), and how they can be used in the clinic (basic science,reimbursement etc.)

• Once a radiotracer has been selected, NOAEL or other mass limit should beestablished and a synthesis developed that enables production of radiotracer dosesof appropriate strength (mCi/mL) and specific activity

• Once the synthesis is established, and no more changes will be made to themethod, the method needs to be qualified for clinical production.

• QC needs to be conducted according to USP<823>, 21CFR212

• Industry and FDA standards should be established so that there is consistentpractices between labs and inspectors

Acknowledgements

• Past and present faculty, staff and students of the Scott Group @ the UM PET Center

• Our many collaborators

• Funding (NIH [R01EB021155], DOE [DE-SC0012484], Alzheimer’s Association [NIRP-14-305669] and Merck)

• Bob Dannals, Mike Kilbourn and Steve Zigler for helpful discussions

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See the Scott Group @SNMMI 2017!

1. F-18 and C-11 Chemistry Challenges, Saturday@8:30, RPSC Categorical, Mile High 2C2. Cu-mediated C-H [18F]Fluorination of Electron Rich Arenes, Young Investigator Award Symposium,

Sunday@12:30, 709/7113. Basic Science Summary Session, Sunday@4:45, Mile-High 1A-C4. Enzyme Substrate Trapped Metabolite Radiotracers Evaluated for the Development of PET/MR

Hybrid Imaging Agents, Monday@5:45, 709/7115. Cu-mediated Radiocyanation with [11C]KCN for the Preparation of [11C]LY2795050, Tuesday@10:00,

709/7116. Nickel(II) Catalyzed Synthesis of Arylboron and Arylstannane [18F]Fluorination Precursors from Aryl

Fluoride Reference Standards, Tuesday@10:30, 709/7117. Automated Synthesis of [68Ga]Gallium Oxine (KP-46) and Preparation of 68Ga-labelled Erythrocytes

for Imaging the Vasculature, Tuesday@1:40, 709/7118. Imaging the Receptor for Advanced Glycation Endproducts with [18F]RAGER, Tuesday@4:00, 709/7119. Binding of [18F]N-Methyl Lansoprazole to Tau Aggregates in Post-Mortem Brain Sections from

Alzheimer’s Disease and Progressive Supranuclear Palsy Patients, Tuesday@4:20, 709/71110. Evaluation of Metal-Protein Aggregate Radioligand [18F]FL2-b by Small Animal PET Imaging and

Autoradiography in AD, ALS and DLB, Sunday@7:00, Posters11. Cu-mediated Nucleophilic [18F]Fluorination of Alkynes, Sunday@7:00, Posters12. Development of PET Tracers for the Dopamine D3 Receptor, Sunday@7:00, Posters13. Synthesis of GAT-1 Selective PET Radioligands, Sunday@7:00, Posters14. Improved Synthesis/Purification of [18F]AV1451, Sunday@7:00, Posters15. Reducing Protodeboronation and Improving [18F]Fluorination of Arylborons, Sunday@7:00, Posters

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