Fully Automated Dual-Run Manufacturing of [¹¹C]PIB on FASTlab

Abstract

This report describes an updated, fully automated method for the production of [¹¹C]PIB on a cassette-based automated synthesis module. The method allows for two separate productions of [¹¹C]PIB, both of which meet all specification for use in clinical studies. The GE FASTlab developer system was used to create the cassette design as well as the controlling tracer package. The method takes 16 minutes from the delivery of [¹¹C]MeOTf to the FASTlab, or 35 minutes from the End of Bombardment; and reliably produces 3547 ± 586 MBq of [¹¹C]PIB in high radiochemical purity (> 98%). This methodology increases the production capacity of radiopharmaceutical facilities for [¹¹C]PIB, and can easily produce 4 batches in a single day with limited infrastructure footprint.

1. Introduction

Alzheimer’s disease (AD) is the most common neurodegenerative disease.[1] AD has the neuropathologic hallmarks of abnormal beta-amyloid (Aβ) and tau protein deposition in the brain.[2] There are now multiple radiotracers available for imaging each of these pathologies in the brain with in vivo positron emission tomography (PET) imaging. [¹¹C] Pittsburg Compound B ([¹¹C]PIB) is the gold standard radiotracer for Aβ imaging in AD.³ [¹¹C]PIB has optimal characteristics of high affinity for Aβ plaques (K_d = 1.4 nM), fast uptake in the brain, and low non-specific binding.[3]

Currently, [¹¹C]PIB is heavily utilized in clinical trials as a non-invasive method of quantifying Aβ levels. The demand is only increasing, and in many research facilities the demand has outstripped the capacity of the manufacturing facilities, mainly due to limited synthesis module capacity. One of our goals is to be able to support multiple production batches in what would normally be a single batch slot. Due to radiation safety constraints, our normal workflow is a single carbon-11 production run in a half-day timeslot. Typically, manufacturing operations for a clinical research dose include: a cleaning task to clean the lines on the module and check the integrity of the system, module setup, and production. In our facility these take several hours, therefore limiting a module to two manufacturing operations per day due to the requirement to let the residual radiation decay (^~3 hours in the case of carbon-11). One potential solution is to increase the available modules; however, this requires that a facility emplace additional hotcells as well, which is extremely difficult due to the space limitations in most facilities. Another solution was to develop a process which allowed for multiple productions of [¹¹C]PIB, while minimizing the other time-consuming steps.

In 2017 Boudjemeline and co-workers published a cassette-based radiosynthesis of [¹¹C]PIB, that avoided the need for HPLC purification.[4] Starting from this work, we elected to pursue a dual-run cassette design to allow for two productions of [¹¹C]PIB on a single cassette. Cassette-based radiosyntheses are extremely attractive for cGMP radiochemistry manufacturing operations, due to their disposable flow-paths, robustness, and simple tech-transfer to other production sites. While this work was taking place, Myburgh and co-workers published a single radiosynthesis of [¹¹C]PIB on the Trasis-AllinOne module.[5] Instead of using a dedicated carbon-11 module, this work transforms the cyclotron-produced [¹¹C]CO₂ into [¹¹C]MeOTf on the cassette and then transfers it to the HPLC loop for standard [¹¹C]PIB radiosynthesis.[6] This work gives a very good radiochemical yield of [¹¹C]PIB with product meeting all QC metrics for clinical research use; however, due to the use of the wet-phase method of [¹¹C]MeOTf preparation, the molar activity was 57 ± 22 GBq/μmol (1540 ± 588 Ci/mmol). While this molar activity is technically sufficient for clinical research, with a radiotracer such as [¹¹C]PIB, image quality is vastly improved when higher molar activities are achieved.[7] Furthermore, as the maximum safe cold mass is 13.4 μg, it is difficult to achieve the ideal dose of 555 MBq (15 mCi) given the volume limitations imposed by the high cold mass once the QC and dose-delivery time is taken into account (^~30 minutes).

The aim of this work was to develop an automated cGMP process for multiple productions of [¹¹C]PIB that is on par or superior to existing methods with regards to reliability, process time, radiochemical purity, impurity levels, isolated yield, and stability.

2. Materials and Methods

2.1. Materials

All chemicals were obtained from commercial sources and were of analytical, ACS, or USP quality (Sigma-Aldrich, USA; APP Pharmaceutical, USA) and were used without further purification. 6-OH-BTA-0 was purchased from Advanced Biochemical Compounds (ABX, Germany) in pre-aliquoted 1 mg fractions. Solid phase extraction (SPE) cartridges (Sep-Pak^® tC18 Plus) were obtained from Waters (Waters^® Association, MA, USA). FASTlab developer kits, including cassette skeletons, vials, and tubing were obtained from GE Healthcare (Waukesha, WI, USA). Sterile empty vials were obtained from either ALK (30 mL, 50 mL) or NucMedCor (250 mL). Sterile filters (Millex-LG, Millex-GV, Pall) were obtained from Millipore-Sigma or Pall Corporation. Sterile vent needles were obtained from Fisher Scientific.

Carbon-11 was produced on a commercial cyclotron (GE Healthcare, PETtrace 880) as [¹¹C]CO₂ by proton bombardment of a gas target containing a mixture of N₂ and O₂ gas (99% N₂ with 1% O₂) to induce the ¹⁴N(p,α)¹¹C nuclear reaction. Typical irradiation current used for the bombardment was 60 μA for 30–35 minutes followed by conversion of the [¹¹C]CO₂ to [¹¹C]MeOTf using the GE TRACERlab FXc Pro.

All radioactivity was measured using a CAPINTEC CRC-15 Dual PET, CRC-15 PET, or CRC-25 Dual PET dose calibrator. The radiochemical purity of the final product [¹¹C]PIB was determined by analytical radio-HPLC with a Phenomenex^® Luna C18(2) column (250 × 4.6 mm), mobile phase: 50% Acetonitrile in 0.1M Ammonium Formate_(aq), flow rate 1.5 mL/min, λ = 254 nm, R_T of [¹¹C]PIB = 5.1 min. Residual solvents were quantified by gas chromatography on an Agilent 7890B instrument. Apyrogenicity tests were performed in-house using Endosafe-Nextgen PTS (Charles River Laboratories Inc.) to ensure that doses of [¹¹C]PIB contained < 8.75 endotoxin units (EU) per mL. ColorpHast^® pH indicator strips (EMD Chemicals Inc.) were used to determine pH of the final product. Final filter integrity testing was performed on the sterilizing filter by standard bubble-point. Sterility testing was performed via direct inoculation into growth media. Stability testing of the [¹¹C]PIB product was performed at periodic times over two hours, testing for radiochemical purity by HPLC and pH.

2.2. In-Process Materials

pH 3.7 Acetate Buffer

450 mL of 200 mM Aqueous Acetic Acid was mixed in a sterile 500 mL bottle with 50 mL 200 mM Aqueous Sodium Acetate. This buffer is stored in the refrigerator is 2–8 °C for up to 3 months.

12.5% Ethanol in Acetate Buffer

A 250 mL sterile vial was equipped with a Pall sterilizing filter and a sterile vent needle. Using a syringe 210 mL of the previously prepared acetate buffer was passed through the sterilizing filter, followed by 30 mL of absolute ethanol. The resulting solution was mixed by manual swirling to ensure thorough mixing. This vial is stored at room temperature for up to 7 days.

15% Ethanol in Acetate Buffer

A 250 mL sterile vial was equipped with a Pall sterilizing filter and a sterile vent needle. Using a syringe 170 mL of the previously prepared acetate buffer was passed through the sterilizing filter, followed by 30 mL of absolute ethanol. The resulting solution was mixed by manual swirling to ensure thorough mixing. This vial is stored at room temperature for up to 7 days.

50% Ethanol in Acetate Buffer

2 mL of absolute ethanol and 2 mL of the previously prepared acetate buffer are added to a 13 mm FASTlab vial. The septum is then affixed and the crimp top secured onto the vial with a crimper. This vial is stored at room temperature for up to 7 days.

FASTlab Developer Cassette Assembly

Cassettes were assembled in-house using FASTlab Developer components as listed in Table 1. After all lines were attached, the cassette skeleton was secured into a hard plastic molded cover.

Table 1:

Pre-Assembled Cassette for [¹¹C]PIB on FASTlab

Position	Description	Production Run Used
1	Empty	N/A
2	Empty	N/A
3	1 mL Syringe	Cassette Cleaning
4	Empty.	N/A
5	42 cm transfer line to position 25	Production Run 2
6	Conical Reservoir (Not Used)	N/A
7	14 cm transfer line to with one end connection replaced with a female luer fitting with 1/16” barb	Production Run 2
8	Male/Male luer fitting	Production Run 2
9	42 cm transfer line	Production Runs 1 & 2
10	42 cm transfer line	Production Runs 1 & 2
11	7.5 mL Syringe	Production Runs 1 & 2, Cassette Cleaning
12	Empty	N/A
13	4 mL Ethanol Vial (13 mm)	Cassette Cleaning
14	50% Ethanol Vial (13 mm)	Production Run 2
15	Water Spike	Cassette Cleaning
16	50% Ethanol Vial (13 mm)	Production Run 1
17	Connection to FXc Pro	Production Runs 1 & 2
18	Male/Male luer fitting	Production Run 1
19	14 cm transfer line to with one end connection replaced with a female luer fitting with 1/16” barb	Production Run 1
20	42 cm transfer line	Production Run 1
21	42 cm transfer line	Production Run 2
22	42 cm transfer line	Production Runs 1 & 2
23	Empty	N/A
24	7.5 mL Syringe	Production Runs 1 & 2, Cassette Cleaning
25	42 transfer line to position 5	Production Run 2

2.3. Final Assembly & Automated Preparation

On the day of production, the 6-OH-BTA-0 was dissolved in methyl ethyl ketone (MEK) at a concentration of 2 mg/mL. The tC18 sep-paks (2) were conditioned with 10 mL of sterile water, 5 mL of MEK, and dried under filtered house air for at least 5 minutes. 150 μL of the 6-OH-BTA-0 solution was loaded onto each tC18 sep-pak via syringe followed by 50 μL of air. The sep-paks are installed with the female side down onto the pre-assembled cassette at positions 8 & 18 with the male end of the sep-paks connected to the 14 cm lines adjacent with the female luer connection. A nitrogen filter is installed onto the left-most connector of the cassette, the orange cap on the water spike is removed, and the output of the TRACERlab FXc Pro connected to position 17. The cassette is then loaded onto the FASTlab along with the water bag. After the cassette test, the 42 cm line at position 22 is connected to a 18G spinal needed in a 50 mL 1X PBS vial, the 42 cm line at position 9 is connected to a 18G spinal needed in the 12.5% ethanol vial, and the 42 cm line at position 10 is connected to a 18G spinal needed in the 15% ethanol vial. All external vials are also equipped with filtered vent needles. An example of the mounted cassette can be seen in Figure 1. The sequence is then started and 1X PBS for dilution of the product is loaded into syringe 3. A full schematic representation of the process is shown in Figure 2.

Figure 1:

Fully Assembled and Mounted Dual-Run [¹¹C]PIB Cassette on FASTlab2

Figure 2:

Schematic representation of the FASTlab2 processes

2.3.1. First synthesis of [¹¹C]PIB

Similar to the previous work[4], the [¹¹C]MeOTf is delivered to the FASTlab at 15 mL/min to position 17 and trapped on the tC18 sep-pak at position 18. Upon completion of the delivery, the precursor and [¹¹C]MeOTf are allowed to react at room temperature for 90 seconds. The sep-pak is then washed with 93 mL of 12.5% Ethanol/Acetate Buffer, followed by 55 mL of 15% Ethanol/Acetate Buffer to wash away unreacted [¹¹C]MeOTf, [¹¹C]MeOH, and remaining 6-OH-BTA-0. The sep-pak is then eluted with 2.5 mL 50% Ethanol/Acetate Buffer into syringe 3 (pre-loaded with 1X PBS). The resulting product solution is transferred to the final vial through a 0.22 μm Millex-LG filter. The sep-pak is flushed with air into syringe 3 and diluted with additional 1X PBS. The solution is transferred to the final vial through the filter, with another dilution of 1X PBS to achieve a 14 mL final volume. The final vial is then transferred to an ISO 5 area for Quality Control. The synthesis time is approximately 35 minutes from end of bombardment.

2.3.2. Cassette Rinsing

Between runs the cassette is automatically rinsed out with water via filling syringes 2 and 3 with water, then then drying the syringes with a combination of nitrogen and vacuum. The cassette manifold is then further washed with water via vacuum and nitrogen push, followed by ethanol. The manifold is then further dried by drying with a nitrogen flow under mild vacuum.

2.3.3. Second synthesis of [¹¹C]PIB

The second synthesis is carried out in a very similar manner to the first procedure. The difference is that the sep-pak in position 8 is utilized and that the waste is channeled through the tubing connection between positions 5 and 25.

3. Results and Discussion

3.1. Initial Testing and Design

Our initial goals were to test the feasibility of using the FASTlab platform for gas-phase reactions, test the coordination of using a secondary module (TRACERlab FXc Pro) to supply [¹¹C]MeOTf to the system, and overcome the size-limited syringes built into the cassette skeleton. Initial testing for gas leaks showed less than 1.5 mL/min of helium leakage from the mass flow controller on the FXc Pro to the cassette exhaust valve, which was consistent across the three lots of FASTlab developer cassettes we tested. With this concern alleviated, we then turned to trapping of the [¹¹C]MeOTf on the tC18 sep-pak (loaded with 6-OH-BTA-0 in 100 μL in MEK). This approach was developed based on the previously published procedure by Boudjemeline[4]. In the previous publication, acetone was used as the reaction solvent, and caused compatibility issues with the plastic manifold. Use of MEK with the FASTlab developer manifolds caused no noticeable compatibility issues. Use of the MEK in our hands proved effective, trapping 33 – 37 GBq(900–1000 mCi) on the sep-pak; which is similar to what we have measured as the typical output for [¹¹C]MeOTf on the FXc Pro.

The cassette is designed to separate the two production pathways as much as possible, while making optimal use of the radiation detector (positions 4, 8, 18, 24), syringes, gas flow, and vacuum positions. For the first production pathway the [¹¹C]MeOTf is delivered into position 17, directed through the sep-pak in position 18, and onwards to the waste bottle (Figure 3). One interesting design parameter that was developed was to use the sep-pak in its inverted configuration. This was optimal due to how the precursor is loaded on the sep-pak, which is from its female end due to the syringe’s male luer connection; by inverting the sep-pak the flow of [¹¹C]MeOTf is from the same direction as the precursor loading, increasing the reaction efficiency. To use an inverted sep-pak, the cassette has a male/male adaptor under the sep-pak and a female-luer adaptor on the tubing connection. Once activity trapping and the labeling reaction have been completed, the washing is commenced. Based on the previous work, we elected to use 92 mL of a 12.5% Ethanol buffered solution, followed by 55 mL of a 15% Ethanol buffered solution. To accomplish this, we attempted several strategies with the goal of a rapid and consistent washing step. First, we tried to use a controlled amount of vacuum from the waste bottle to pull solution from bottle in position 9; however, despite numerous attempts we were unable to get a consistent volume of wash solution. Second, we attempted to augment the vacuum pull by pressurizing the solution bottle at a controlled pressure. Again, however, we were unable to get a consistent volume across multiple runs, and were forced to move onto a more conventional strategy using multiple syringe pushes for the sep-pak washing. The rationale for using the previous two methods was to avoid using the 7.5 mL (maximum capacity) syringe to move such a large volume and the required time to do so; however, in the end we were able to optimize use of the syringe to perform the rinsing in a rapid fashion by minimizing the time of the syringe pushes & loading.

Figure 3:

Cassette Layout

With the initial testing complete and cassette design selected, radioactive testing could begin. After optimization of the syringe movement speed and reaction time, we were able to develop an effective control sequence for the production of [¹¹C]PIB (Table 2). While the precise syringe movement speed isn’t available for direct control, reducing the number of steps for the syringe to move effectively increases the syringe speed.

Table 2:

Initial Testing Results

Sequence Changes	Product Activity	Synthesis Time (After Delivery of [11C]MeOTf)
Initial (0.2)	2749 MBq (74.3 mCi)	19 min
Increased Syringe Speed	3855 MBq (104.2 mCi)	15.2 min
Increase from 0.1 to 0.15 mg of Precursor	4466 MBq (120.7 mCi)	15.2 min
Standard Loop Method	3330 – 4810 MBq (90 – 130 mCi)	~16 min

Once a sequence that produced high levels of product was developed, we then turned to optimizing the reagent selection. Attempts to remove the acetate buffer from the ethanol eluent proved inferior, either due to the [¹¹C]PIB not eluting, or being stuck on the final filter. We also explored different amounts of precursor being loaded onto to the sep-pak, and were able to achieve optimal results with 0.3 mg of 6-OH-BTA-0 loaded in 150 μL of MEK. Exploration of the final filter confirmed that the Millex-LG was the optimal filter with only 4% of the activity retained on the filter, while a vented Millex GV retained 19%, and 89% retained was on a vented Millex-GS. For the first production pathway, robust and reliable results were obtained with the final control sequence (Table 3).

Table 3:

Results from Testing of the First Production Pathway

Release Criteria	Specification	Test 1A	Test 2A	Test 3A
Appearance	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates
Filter Integrity	> 40 psi	51 psi	52 psi	52 psi
pH	4 – 8	4.5	4.5	4.5
Radiochemical Purity	≥ 90%	> 99.9 %	98.4 %	99.2 %
Molar Activity	≥ 18.5 GBq/μmol (≥ 500 Ci/mmol)	380 GBq/μmol (10282 Ci/mmol)	415 GBq/μmol (11238 Ci/mmol)	422 GBq/μmol (11403 Ci/mmol)
Residual Solvent	≤ 5000 ppm MEK	0 ppm	7.58 ppm	6.84 ppm
Formulation	NMT 10% EtOH	7.8 %	7.8 %	7.2 %
Total Chemical Impurities	NMT 50 μg/dose	0.083 μg/mL	0.240 μg/mL	0.202 μg/mL
Activity in Final Vial		3.66 GBq (99.0 mCi)	4.55 GBq (122.9 mCi)	3.65 GBq (98.7 mCi)
Concentration		295 MBq/mL (7.97 mCi/mL)	385 MBq/mL (10.4 mCi/mL)	296 MBq/mL (8.0 mCi/mL)

Similar optimizations were undertaken for the second production pathway. This pathway directed the [¹¹C]MeOTf from position 17 to the sep-pak at position 8, out through the tubing at position 7, to the cassette exhaust through the tube from position 5 to position 25, and then to the waste bottle. This virgin pathway allows for complete separation from the first production pathway. After the reaction, the sep-pak washing used Syringe 2 for the washing, with the outflow passing through the tubing connection from position 5 to 25, and then onwards to the waste. The product was eluted from the sep-pak (position 8), through the tubing from position 5 to 25, and then into Syringe 3 (pre-loaded with 1X PBS). The product was transferred to the final vial at position 21 through a sterilizing filter, followed by additional washing with 1X PBS. Testing demonstrated that production along this pathway was also robust and reliable (Table 4).

Table 4:

Results from Testing of the Second Production Pathway

Release Criteria	Specification	Test 1B	Test 2B	Test 3B
Appearance	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates	Clear, Colorless, No Particulates
Filter Integrity	> 40 psi	48 psi	47 psi	49 psi
pH	4 – 8	4.5	4.0	4.0
Radiochemical Purity	≥ 90%	99.6 %	99.5 %	98.4 %
Molar Activity	≥ 18.5 GBq/μmol (≥ 500 Ci/mmol)	1164 GBq/μmol (31450 Ci/mmol)	747 GBq/μmol (20181 Ci/mmol)	1166 GBq/μmol (31510 Ci/mmol)
Residual Solvent	≤ 5000 ppm MEK	16 ppm	16 ppm	16 ppm
Formulation	NMT 10% EtOH	6.8 %	6.7 %	6.8 %
Total Chemical Impurities	NMT 50 μg/dose	0.264 μg/mL	0.354 μg/mL	0.268 μg/mL
Activity in Final Vial		3.85 GBq (104 mCi)	3.7 GBq (100 mCi)	2.68 GBq (72.5 mCi)
Concentration		294 MBq/mL (7.94 mCi/mL)	310 MBq/mL (8.39 mCi/mL)	216 MBq/mL (5.83 mCi/mL)

With the sequence for both production pathways developed, cleaning of the cassette manifold was developed to ensure that no degradation of the second production sequence occurred. Initial attempts at cleaning proved insufficient, with residual buffer salts remaining. Moving towards a cleaning sequence of first water, then ethanol, followed by extensive drying with nitrogen gas flow and vacuum. After several iterations, an effective cleaning sequence was developed and the process fully qualified.

The product validation campaign consisted of three consecutive production runs of two batches each meeting all quality metrics; each of the two batches was prepared with a six-hour waiting period between the two runs to demonstrate the stability of all components for an extended time between runs, with no noted degradation in yield or other parameter (Table 5). All runs produced sufficient activity to allow for at least one dose administration of 555 MBq (15 mCi), allowing for sufficient time for the quality control tests (25–30 minutes). With a maximal bombardment and conversion from [¹¹C]CO₂ to [¹¹C]MeOTf providing 74 GBq of [¹¹C]MeOTf, multiple doses of [¹¹C]PIB would be achievable; depending on scanner availability. Total synthesis time compares favorably to conventional methods from end of bombardment to the finished final vial.

Table 5:

Results from Production Validation Campaign

Release Criterial	Specification	Qual Runs 1A & 1B	Qual Runs 2A & 2B	Qual Runs 3A & 3B
Appearance	Clear, Colorless, No Particulates	Clear, colorless, no particulates	Clear, colorless, no particulates	Clear, colorless, no particulates
Radiochemical Identity (% difference from Ref Std) by HPLC	NMT 10%	1.64 % 2.09 %	2.85 % 2.74 %	2.87 % 2.62 %
Radiochemical Purity (%) (HPLC)	≥ 90%	99.75 % 99.68 %	98.63 % 98.44 %	98.71% 98.70 %
Total Chemical Impurities	NMT 50 μg/dose	0.1205 μg/mL 0.0628 μg/mL	0.0343 μg/mL 0.0523 μg/mL	0.0882 μg/mL 0.0236 μg/mL
Molar Activity	≥ 18.5 GBq/μmol	555 GBq/μmol 627 GBq/μmol	816 GBq/μmol 970 GBq/μmol	985 GBq/μmol 996 GBq/μmol
Bacterial Endotoxin Levels (EU/mL)	NMT 8.75 EU/mL	< 1.00 EU/mL < 1.00 EU/mL	< 1.00 EU/mL < 1.00 EU/mL	< 1.00 EU/mL < 1.00 EU/mL
Radionuclidic Identity (t1/2, minutes)	19.38 – 21.42	20.35 min 20.35 min	20.27 min 20.40 min	20.251 min 20.347 min
Residual Ethanol Level, ppm (NMT 78,900)	NMT 78900 ppm (10% EtOH)	59811 ppm 36359 ppm	60437 ppm 51539 ppm	58969 ppm 52953 ppm
Residual 2-Butanone Level, ppm (NMT 5000)	≤ 5000 ppm	7.083 ppm 14.916 ppm	9.358 ppm 15.009 ppm	7.099 ppm 23.610 ppm
pH	4 – 8	4.0 4.0	4.0 4.0	4.0 4.0
Filter Integrity	> 40 psi	Pass Pass	Pass Pass	Pass Pass
Sterility (Observed growth after 14 d)	No Growth	No Growth No Growth	No Growth No Growth	No Growth No Growth
Amount of Product	Report	3922 MBq 3485 MBq	2579 MBq 4240 MBq	3807 MBq 3249 MBq

The dual-run manufacturing process developed herein has several significant advantages over conventional methods. First, its use of disposable cassettes allows for straightforward technology-transfer to interested manufacturing sites; as well as much more straightforward cGMP compliance with the relevant regulations in the manufacturing site’s area of operations.[8] The use of a cassette-based approach also eliminates the need for cleaning of the production module prior to use, resulting in a significant time-savings for the operator. Furthermore, having the ability to perform two batches, either back-to-back or separated by as much as six-hours allows for an increased manufacturing capacity; permitting up to four batches in a single day with the currently developed workflow. This allows for two morning batches for subject administration, making those subjects available to receive a fluorine-18 or additional carbon-11 PET-scan in the afternoon; enabling amyloid and tau scans to be acquired in a single clinic visit. While this method does require the use of two synthesis modules, current module technology (GE TRACERlab FX₂C) can supply up to four cassette-modules, reducing the infrastructure burden.

4. Conclusions

We have successfully validated a dual-run cassette-based method for manufacture of [¹¹C]PIB under current Good Manufacturing Practice (cGMP) requirements. Production time and radiochemical yields are comparable to typical automated procedures. The optimized procedure proved to be robust and reliable over three consecutive dual-run productions. The [¹¹C]PIB produced meets all release criteria for clinical research, and especially has excellent molar activity and low chemical impurity levels. Using this method, it is possible to meet the increasing [¹¹C]PIB manufacturing demands with existing infrastructure.