PRODUCTION AND QUALITY CONTROL OF RADIOPHARMACEUTICALS

RAYMOND TAILLEFER, M.D. FRCP(c), ABNMDIRECTOR, DEPARTMENT OF NUCLEAR MEDICINEHOPITAL DU HAUT-RICHELIEU,CANADA

Disclosures to Report:Grant Research Support: Lantheus Medical ImagingConsultant: Lantheus Medical Imaging

OVERVIEW

1- PRODUCTION OF RADIONUCLIDES

2- RADIOISOTOPE GENERATORS

3- PREPARATION OF RADIOPHARMACEUTICALS

4- QUALITY CONTROL

5- Tc-99m «COLD KIT»

PRODUCTION OF RADIOISOTOPES

GENERATORNUCLEAR REACTOR

CYCLOTRON

Primary sources

Secondarysource

Nuclear bombardment

Hit nucleus of stable atomwith sub-nuclearparticles: neutrons,protons, alpha particles etc.

• There are two main methods of performing this bombardment

• 1. Inserting target in a nuclear reactor - fine for longer-lived isotopes

• 2. Using a charged-particle accelerator called a 'cyclotron'

electron

neutron

proton

Radioisotopes in Nuclear Medicine

– REACTOR– Molybdenum-99 (f)

• Technetium-99m– Iodine-131– Phosphorus-32– Yttrium-90– Samarium-153– Strontium-89 (f)– Iodine-125– Cr-51– C-14– Xe-133 (f)– Sr-90 (f) -> Y-90

• Linear Accelerator or High Energy Cyclotron– Thallium-201– Indium-111– Iodine-123– Gallium-67– Sr-82 -> Rubidium-82– Co-57

• Low Energy Cyclotron– Fluorine-18– Carbon-11– Nitrogen-13– Oxygen-15

20

Production-Short Hand Equation

68Zn (p, 2n) 67Ga

Target

Bombarding particle

Emitted particle(s)

Product

Reactor Produced Radioisotopes

Nuclear Fissionn4 Sn Mo U n U 1

0133

5099 42

236 92

10

23592 ++→→+

• Heavy nuclei (235U) • Absorption of a thermal neutron (E ~ 0.03 – 100 eV)• Break up (fission) into two nuclei of similar atomic weight • Neutrons are produced which can be absorbed by other

heavy nuclei • Neutron/Proton ratio is high• Process continues until all the nuclear fuel is spent • Products different atomic number• High specific activity

Neutron Capture vs. Fission

• 98Mo42 (n,• ) 99Mo42

– Cost less to prepare– Low specific activity

• 75mCi/mg

– Low concentration

• 235U92 (n,f) 99Mo42

– Costs more to prepare– High specific activity

• 500Ci/mg

– Smaller column– Less shielding– Higher concentration

Reactors producing radionuclides used in medicine

• Belgium• France• Netherlands• South Africa• Canada

• Australia

Processes of 99Mo/99mTc generator

nMo-99

+

Impuritieshttp://www.nci.org/index.htm

•Reactor sites responsible for producing radionuclide

•Processing plant responsible for sterile, pyrogen free product

•Carrier Free; High specific activity

•<0.05uCi I131 & Ru103; <0.0006uCi Sr89; <0.1uCi others / mCi Tc99m

PREPARATION OF RADIOPHARMACEUTICALS:

RADIONUCLIDE USED AS A TRACER IN MEDICINE, PRESENTED IN A SPECIFIC CHEMICAL FORM WHICH CONTROLS ITS BIOLOGICAL FATE WHEN ADMINISTERED TO THE PATIENT.

1- EXTRACTION OF THE RADIONUCLIDE FROM THE BULK OF THE TARGET SUBSTANCE

PREPARATION OF RADIOPHARMACEUTICALS:

RADIONUCLIDE USED AS A TRACER IN MEDICINE, PRESENTED IN A SPECIFIC CHEMICAL FORM WHICH CONTROLS ITS BIOLOGICAL FATE WHEN ADMINISTERED TO THE PATIENT.

1- EXTRACTION OF THE RADIONUCLIDE FROM THE BULK OF THE TARGET SUBSTANCE

2- PURIFICATION TO REMOVE UNWANTED CHEMICAL AND RADIONUCLIDE IMPURITIES

PREPARATION OF RADIOPHARMACEUTICALS:

RADIONUCLIDE USED AS A TRACER IN MEDICINE, PRESENTED IN A SPECIFIC CHEMICAL FORM WHICH CONTROLS ITS BIOLOGICAL FATE WHEN ADMINISTERED TO THE PATIENT.

1- EXTRACTION OF THE RADIONUCLIDE FROM THE BULK OF THE TARGET SUBSTANCE

2- PURIFICATION TO REMOVE UNWANTED CHEMICAL AND RADIONUCLIDE IMPURITIES

3- CHEMICAL CONVERSION OF THE PURE RADIONUCLIDE INTO A BIOLOGICALLY SPECIFIC FORM

PREPARATION OF RADIOPHARMACEUTICALS:

RADIONUCLIDE USED AS A TRACER IN MEDICINE, PRESENTED IN A SPECIFIC CHEMICAL FORM WHICH CONTROLS ITS BIOLOGICAL FATE WHEN ADMINISTERED TO THE PATIENT.

1- EXTRACTION OF THE RADIONUCLIDE FROM THE BULK OF THE TARGET SUBSTANCE

2- PURIFICATION TO REMOVE UNWANTED CHEMICAL AND RADIONUCLIDE IMPURITIES

3- CHEMICAL CONVERSION OF THE PURE RADIONUCLIDE INTO A BIOLOGICALLY SPECIFIC FORM

4- ADDITION OF THE NECESSARY EXCIPIENT TO MAKE THE PREPARATION SUITABLE FOR ADMINISTRATION TO THE PATIENT

PREPARATION OF RADIOPHARMACEUTICALS:

RADIONUCLIDE USED AS A TRACER IN MEDICINE, PRESENTED IN A SPECIFIC CHEMICAL FORM WHICH CONTROLS ITS BIOLOGICAL FATE WHEN ADMINISTERED TO THE PATIENT.

1- EXTRACTION OF THE RADIONUCLIDE FROM THE BULK OF THE TARGET SUBSTANCE

2- PURIFICATION TO REMOVE UNWANTED CHEMICAL AND RADIONUCLIDE IMPURITIES

3- CHEMICAL CONVERSION OF THE PURE RADIONUCLIDE INTO A BIOLOGICALLY SPECIFIC FORM

4- ADDITION OF THE NECESSARY EXCIPIENT TO MAKE THE PREPARATION SUITABLE FOR ADMINISTRATION TO THE PATIENT

5- TESTING THE QUALITY OF THE FINAL PRODUCT

99Mo - 99mTc- GENERATOR

• APPLICATION OF SHORT-LIVED RADIONUCLIDE RESTRICTED TO A PLACE CLOSE TO ITS SOURCE.

• THE SHORTER THE T½, THE CLOSER TO THE SOURCE ARE THE PRACTICAL LIMITS

• PARENT ( LONG-LIVED RN) DECAYS TO FORM A DAUGHTER (SHORTER- LIVED RADIONUCLIDE)

• SUITABLE MEANS FOR SEPARATING THE TWO SPECIES.

• PARENT = TRANSPORTABLE SOURCE OF THE DAUGHTER RADIONUCLIDE

Concept of a Radioisotope Generator

Requires suitably matched “parent” & “daughter” isotopes

Parent isotopeis bound to a

matrix

Parent isotopedecays to its

daughter Daughter iseluted fromthe column

99Mo

99mTc

99Mo

99Mo

99mTc

MOST IMPORTANT GENERATOR

• SYSTEM USED FOR PROVISION OF 99mTc FROM FISSION PRODUCT 99Mo.

•U (n, fission) 99Mo•98Mo (n,gamma) 99Mo•100Mo (p, gamma) 99Mo

• DAILY ACCESS TO 99mTc (short T½ = 6 hours).

• ONCE-WEEKLY DELIVERY OF 99Mo (T½ = 66 hours).

• EXTRACTION OF 99mTc BY SIMPLE COLUMN CHROMATOGRAPHY.

99Mo - 99mTc- GENERATOR SYSTEM

• RADIOACTIVITIES OF BOTH 99Mo AND 99mTc ARE CONTINUALLY CHANGING.

• 99Mo LEVEL DECREASES BY RADIOACTIVE DECAY.

• 99mTc LEVEL : INFLUENCED BY BOTH GROWTH AND DECAY EFFECTS.

• LEVEL OF 99mTc: COMPLEX EXPONENTIAL FUNCTION OF TIME

• “TRANSIENT-EQUILIBRIUM”

DECAY-GROWTH OF 99Mo-99mTcTransient equilibrium

SEPARATION OF 99mTc FROM 99Mo

• BASED ON THE DIFFERENCES IN THE PHYSICAL OR CHEMICAL PROPERTIES OF 99Mo and 99mTc.

• COLUMN CHROMATOGRAPHY : 99Mo IS IMMOBILIZED ON AN ALUMINA COLUMN.

• PASSAGE OF A SALINE SOLUTION THROUGH THE COLUMN WILL REMOVE (ELUTE) THE 99mTc AS A SODIUM PERTECHNETATE SOLUTION.

• GEL GENERATOR : COLUMN OF AMORPHOUS ZIRCONIUM MOLYBDATE.

99Mo/99mTc Generator

• 99Mo adsorbed onto alumina column having two ionic charges

• 99Mo decays into 99mTc

• 99mTcO4- form (pertechnetate) has one ionic charge

Terminology Related to Alumina Column 99Mo/99mTc Generators

• Eluting or “Milking” • Eluent • Eluate • Ion Exchange Column • Fractional Elution • Specific Concentration• Elution Efficiency

•Elution with NS removes the weakly bound 99mTcO4

-

leaving the 99MoO42- on

the column

•The eluent is Na99mTcO4

•(sodium pertechnetate)

Tc-99m “Dry Column” Generator

Quality Control of Mo99/Tc99m Generator Eluates

By manufacturer: Sterility, pyrogens, and radionuclidic contaminants in Mo-99

By user after each elution:

• Mo-99 radionuclide impurity

• Alumina (Al+3) present in eluate

• Hydrolyzed Reduced Tc-99m (99mTcO2)

QUALITY CONTROL OF 99mTc-ELUATE

1- 99Mo BREAKTHROUGH.

2- OTHER RADIONUCLIDE CONTAMINATION.

3- ALUMINUM BREAKTHROUGH.

4- pH.

OTHER RADIONUCLIDE CONTAMINATION

• GENERATOR USING FISSION-PRODUCED 99Mo.

• USP LIMITS :•131 I : 0.05 µci/mci ( 0.05 Bq / kBq).•103 Ru : 0.05•89 Sr : 0.0006•90 Sr : 0.0006•other Beta and gamma emitting : <0.01%

• MULTICHANNEL PULSE HEIGHT ANALYZER.

• PERFORMED BY MANUFACTURER.

99Mo BREAKTHROUGH

• ORIGINATES FROM THE SMALL QUANTITY OF 99Mo THAT MAY BE ELUTED WITH 99mTc.

• USP : 0.15 µCi 99Mo / mCi of 99mTc ( 1.5Bq / 10 kBq).

• DETECTION OF 740 AND 780 Kev PHOTON OF 99Mo.

• DOSE CALIBRATOR

• COLORIMETRIC TEST: ADDITION OF PHENYLHYDRAZINE TO THE ELUATE: COLOR CHANGE.

Radionuclide Purity Test “Moly Breakthrough Test”

• Dose Calibrator • 6mm lead “Moly

Canister”• Subtract background

6mm

Mo99 740keV & 780keV

Tc99m 140keV

ALUMINUM BREAKTHROUGH

• DERIVED FROM ALUMINA BED OF THE GENERATOR.

• INTERFERENCE WITH THE PREPARATION OF VARIOUS RADIONUCLIDES

• 99mTc-Sulfur colloid• 99mTc- red blood cells

• USP LIMITS : <10 µg Al/ml.COLORIMETRIC METHOD.

• EXCESSIVE AMOUNT OF ALUMINUM = LACK OF STABILITY OF THE COLUMN.• pH : normal : 4.5 to 7.5

Chemical impurity

• Paper coated with aurintricarboxylic acid

• Forms a pink precipitant with aluminum ion (Al+3)

• Control standard (10ug/ml)

• 10ug/ml • USP limit for aluminum

ion content

99mTc- “COLD” KIT

• VERSATILE MEANS OF ENABLING THE PREPARATION OF A WIDE VARIETY OF PRODUCTS.

• GLASS VIAL WITH SPECIFIED QUANTITIES OF REAGENTS ( FREEZE DRIED).

• LONG SHELF-LIFE ( > 12 MONTHS).

• REDUCING AGENT: TIN (STANNOUS CHLORIDE).

• ANTIOXIDANT ( ASCORBIC OR GENTISIC ACID).

• REDUCTION FROM OXIDATION STATE (VII) TO LOWER OXIDATION STATE ( III OR IV).

REAGENT VIAL OR « KIT »

RADIOCHEMICAL PURITY

• FRACTION OF THE TOTAL RADIOACTIVITY IN THE DESIRED CHEMICAL FORM IN THE RADIOPHARMACEUTICAL.

• RADIOCHEMICAL IMPURITIES ARISE FROM DECOMPOSITION DUE TO :

•ACTION OF SOLVENT•CHANGE IN TEMPERATURE OR pH .•OXIDIZING OR REDUCING AGENTS•RADIOLYSIS OR LIGHT.

RADIOCHEMICAL PURITY

• FREE 99mTcO4- , HYDROLYZED 99mTc.

• NUMBER OF ANALYTICAL METHODS:•PRECIPITATION•PAPER, THIN-LAYER, GEL CHROMATOGRAPHY.•PAPER AND GEL ELECTROPHORESIS.•HIGH PERFORMANCE CHROMATOGRAPHY.

ASCENDING CHROMATOGRAPHY

Solvent front Origin

Na99mTcO4

95% 99mTcO2 * H20 (colloid)5%

Radiochemical purity

CHROMATOGRAPHIC ANALYSIS

SYSTEM A : 99mTco4 migrates at the solvent front, 99mTc-MDP and 99mTcO2 at the origin.

SYSTEM B : Only 99mTcO2 remains at the origin.

ELECTROPHORESIS CHAMBER

Direct current applied, enabling migration of radioactive ions applied to the cellulose acetate medium.

CHEMICAL PURITY

• FRACTION OF THE MATERIAL IN THE DESIRED CHEMICAL FORM.

• PRINCIPAL UNDESIRABLE CHEMICAL CONTAMINANT IN A 99mTc- GENERATOR ELUATE: ALUMINUM.

BIOLOGICAL TESTS

• STERILITY : ALL PREPARATIONS MUST BE STERILIZED.

• APYROGENICITY:•PYROGEN: POLYSACCHARIDES OR PROTEINS.•CHILLS, MALAISE, FATIGUE, NAUSEA….•RABBIT TEST, LAL TEST.•TOXICITY

Compounding with Tc-99m

• Many oxidation states• +7 stable (Na+1:Tc+7:O4

-8) • Kits contain stannous chloride (Sn+2)• Reducing agent• Liquid Sn+2 very susceptible to oxidizing• When Tc99m is in lower than +7 you must

have a ligand available

Tc99m-sestamibicommercially available kit

– 2-methoxy isobutyl isonitrile copper tetrafluoroborate 1mg (ligand)

– Sodium citrate dihydrate 2.6mg (trans-chelate)

– L-cysteine HCL monohydrate 1mg (accelerator )

– Mannitol 20mg (solubilizing agent )

– Stannous Chloride 0.025-0.075mg (reducing agent)

Tc99m-sestamibi

• Reconstituted w/150mCi TcO4- in 3mls• Boil for 10 minutes, cool, QC• QC: Baker-flex Aluminum Oxide plastic TLC

plates using 100% ethanol as the solvent phase

• % Tc99m-sestamibi= top counts/ total counts• Package insert procedure takes about 40

minutes

Tc99m-tetrofosmincommercially available kit

• Commercially available kit– Tetrofosmin 0.23mg (ligand)– Stannous chloride 30ug (reducing agent)– D-gluconate 1mg (trans-chelate)– Sodium bicarbonate 1.8mg (buffer)

• Reconstitute with 240mCi of TcO4- in a volume of 8mls with a venting needle is very important for stability

• Tc99m concentration is very important for stability

• Incubate at room temperature for 15min.

Tc99m-tetrofosmin

QC testing of 99mTc-tetrofosmin

Instant thin-layered chromatography (ITLC)• Recommended by the manufacturer• ITLC/SG strip (20cm x 1cm) • 35:65 acetone:dichloromethane mixture as mobile phase • Drawbacks:

– Toxic solvent dichloromethane– Factors affecting QC results:

• sample drop size, the condition of the SG strip, the freshness and the exact ratio of acetone:dichloromethane

– requires 20 to 50 minutes

SECULAR EQUILIBRIUM

• Secular Equilibrium– Parent half-life>>>

daughter half-life

• Generator produced from the parent Sr-82 (T1/2 = 25 days) (Secular equilibrium)

• T1/2 = 75 sec• Rubidium cation• Na-K ATPase pump

• Dose: 50-60mCi infused over 20-30 seconds

• Imaging 90sec post Automated infusion

Rubidium-82 (CardioGen-82®)

Rubidium-82 (CardioGen-82®)

• Generator useful for 4-6 weeks

• Available w/ three month notice to Bracco

• Strontium-82 generator T1/2=25 days, (Rb-82 75sec)

• Disadvantage: High energy (3.15 Mev max) travels farther from site of origin (12mm) before annihilation, decreasing intrinsic resolution.

HAVE I OVERLOADED YOU ??