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Preparation of patient doses of 177 LuDOTATATE using indigenously produced 177 Lu : The Indian experience
Tapas Das, Sudipta Chakraborty, Sharmila Banerjee, Meera Venkatesh Radiopharmaceuticals Division
Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, INDIA Email: [email protected]
TECHNICAL MEETING ON THERAPEUTIC RADIOPHARMACEUTICALS 1620 NOVEMBER 2009
VIENNA
DOTATATE as the peptide vector for PRRT
(Thr)
(Thr)
(Lys)
(Trp)
(Tyr)
(Cys)
(Cys)
(Dpheala)
H
H OH H 3 C O
HN
S
O NH
H 3 C
H H H
NH 2
HN
O
H
H O HN
N OH
O
OH
HN
H
O
NH S H
H
O
NH
N
N N
N COOH
HOOC
HOOC
O
NH
OH
COOH
The Potential of both DOTATATE as a vector for PRRT and 177 Lu as an ideal therapeutic radioisotope unravelled
Thus 177 LuDOTATATE was envisaged as an agent
Favourable features of DOTATATE for PRRT
q Only effective treatment known for neuroendocrine tumors and presently available in a limited number of countries with prohibitively high cost (~$40,000)
q Somatostatin receptors Overexpressed in a variety of cancers Ø Majority of neuroendocrine tumors Ø Neuroblastomas Ø Some medullary carcinomas Ø Some prostate cancer Ø Small cell lung cancer
q Octreotide analogue for targeting somatostatin receptors Ø High binding affinity with sst 2 and sst 5 Ø DOTATATE binding with sst 2 is 9 times better than DOTATOC Ø Retention of receptor binding potential of DOTATATE post radiolabeling
The challenges in preparing 177 LuDOTATATE using indigenously produced 177 Lu
r Production of 177 Lu with required specific activity using our medium flux research reactors
r Preparation the radiolabeled agent with adequately high specific activity in order to deposit sufficient activity in the cancerous lesions without saturating the limited number of receptors
r Adequate radiochemical purity and stability postpreparation r Since specific activity of 177 Lu available at the time of
preparation of the agent varies considerably Ø The need for an optimized labeling protocol Ø More importantly with respect to the amount of peptide, in order that it can be prepared with high radiochemical purity using minimum amount of DOTATATE
4
This means …
5
Minimum amount of Peptide High specific activity
Adequate stabilty after preparation
Striking a balance between peptide amount and radiochemical stability
Production of 177 Lu by direct neutron activation
Radionuclidic impurity
q 175 Lu (n,γ) 176m Lu (β , 3.7 h) 176 Hf (stable) E β(max) = 1.2 MeV E γ = 88 keV
Ø 1 d cooling post EOB ensures no 176m Lu in 177 Lu
q 176 Lu (n,γ) 177m Lu (β , 160.5 d) 177 Hf (stable) E β(max) = 0.2 MeV E γ = 128, 153, 228, 378, 414, 418 keV
Ø 177m Lu only possible RN impurity present in 177 Lu
Percentage RN purity of the 177 Lu produced by direct neutron activation
q Radionuclidic purity of the 177 Lu produced depends on Ø Time of irradiation Ø Neutron flux at which irradiation is carried out
q The average level of radionuclidic impurity burden in 177 Lu due to 177m Lu found to be 150 250 nCi of 177m Lu / 1 mCi of 177 Lu (5.5 9.25 kBq / 37 MBq) at EOB
q Radionuclidic purity of 177 Lu achievable is 99.975% to 99.985% depending upon the irradiation conditions
Specific activity vs. irradiation time
8 7 6 5 4 3 2 1 0
100
75
50
25
0
Time of irradiation (in terms of halflife)
%Maximum
obtainable activity
28 21 14 7 0
325
300
275
250
225
200
175
150
125
100
Duration of irradiation (d)
Specific activity
of 17
7 Lu (GBq.mg
1 )
Irradiation of enriched Lu 2 O 3 at 1 × 10 14 n.cm 2 .s 1
Standard activity vs. irradiation time curve
Irradiations with 82% enriched target
q Irradiations (14 batches) with 82% enriched (in 176 Lu) Lu 2 O 3 target
q Flux 7 ×10 13 to 1×10 14 n/cm 2 .s
q Irradiation period – 21 days
q Typical values of specific activities obtained are between 7401480 GBq/mg (2040 Ci/mg)
q Corresponds to 18% 36 % of the maximum achievable specific activity
q The specific activity of 177 Lu obtained was significantly higher compared to the theoretically calculated value under the irradiation condition
Growth of 177 Lu production in India
2006 [1] 2007 [9] 2008 [9] 2009 [10*] 0
200
400
600
800
1000
*Production upto the month of October is considered for 2009
177 Lu activity produced (in
GBq
)
Year (Number of batches)
Steady Growth in Production
Formulation of patient dose of 177 LuDOTATATE (typically ~ 150200 mCi, 5.557.40 GBq)
Step I. Amount of Lu required to obtain that dose was calculated from the specific activity of 177 Lu after the necessary decay correction
Step II. The requirement of DOTATATE was subsequently determined considering that DOTATATE : Lu molar ratio to be 4:1 (previously optimized)
Step III. Required volume of DOTATATE solution (1 mg/mL in de ionized water) and 177 LuCl 3 were added to 0.1 M ammonium acetate buffer (pH ~ 5) containing 40 mg/mL gentisic acid (volume 3 times of the total volume of DOTATATE and 177 LuCl 3 solution
Step IV. The preparation was then subsequently heated in at 90 ο C for 60 min at pH 45
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A typical example
• For preparation of a 200 mCi (7.40GBq) patient dose of 177 LuDOTATATE
– Amount of Lu – 8 µg (since sp. act available at this time is 25Ci/mg, 925 GBq/mg) which is equivalent to 0.045 µM Lu.
– The molar ratio of DOTATATE and Lu need to be 4:1 in the preparation • The amount of DOTATATE which will be required in this case will be 260 µg (molecular weight of DOTATATE is 1436
• The concentration of stock solution of DOTATATE is 1 µg/µLtherefore 260 µL of the stock solution has to be used.
• The radioactive concentration of 177 Lu at the time of preparation is 1Ci/mL (37 GBq/mL), 200 µL of 177 LuCl 3 will be required to have 200 mCi (7.40 GBq) of Lu activity.
• Therefore, the buffer requirement will be (260 + 200) × 3 µL = 1380 µL i.e. ~1.4 mL.
• Hence, for the actual preparation, 260 µL of DOTATATE stock solution will be added to 1.4 mL of 0.1 M ammonium acetate buffer containing 56 mg of gentisic acid (stock solution in buffer contains 40 mg/mL), followed by 200 µL of 177 LuCl 3 .
Formulation of patient dose of 177 LuDOTATATE
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Composition of 200 mCi patient dose of 177 LuDOTATATE for different 177 Lu specific activity
177 Lu specific activity
Amount of lutetium*
Amount of DOTA TATE#
Volume of 0.1 M NH 4 OAc (pH ~5)
Amount of gentisic acid
177 LuDOTA TATE specific
activity
20 Ci/mg 10.0 µg
(0.057 µM)
326 µg
(0.228 µM)
1.6 mL 64 mg 881 mCi/µM
25 Ci/mg 8.0 µg
(0.045 µM)
260 µg
(0.180 µM)
1.4 mL 56 mg 1105 mCi/µM
30 Ci/mg 6.7 µg
(0.038 µM)
219 µg
(0.152 µM)
1.3 mL 52 mg 1311 mCi/µM
35 Ci/mg 5.7 µg
(0.032 µM)
186 µg
(0.128 µM)
1.2 mL 48 mg 1544 mCi/µM
40 Ci/mg 5.0 µg
(0.028 µM)
163 µg
(0.112 µM)
1.1 mL 44 mg 1762 mCi/µM
*Radioactive concentration 1 mCi/µL # Concentration 1 mg/mL in deionized water
Salient Features
q Available specific activity of 177 Lu varied over a wide range during the actual preparation of the patient doses in different batches therefore composition of the each constituents were varied accordingly in order to prepare the agent with maximum possible specific activity
q The amount of DOTATATE required to prepare a patient dose of 200 mCi (7.40 GBq) varied from 175350 µg and a patient dose is typically achieved in a total volume of 1.52.2 mL
q The radiochemical purity of the 177 LuDOTATATE complex was determined to be 98.25±1.1%
q The agent was obtained with a specific activity of 0.571.14 Ci/mg (21.1442.29 GBq/mg) or 0.82×1031.63×103 Ci/mMole (30.2360.46 TBq/mMole)
Quality Control Methods
15
0 1 2 3 4 5 6 7
100
80
60
40
20
0
Migration from point of spotting (cm)
%Radioactivity
177 LuDOTATATE 177 LuCl 3
0 300 600 900 1200 1500 1800 0
200
400
600
800
1000
CPS
Retention time (s)
PC using 50% aqueous acetonitrile HPLC using C18 reverse phase column
Our Partners in Clinical trials
• Dr. C. S. Bal, All India Institute of Medical Sciences, New Delhi, India
• Dr. K.G. Kallur, Bangalore Institute of Oncology, Bangalore, India
• Dr. B. A. Krishna, Hinduja Hospital, Mumbai, India
• Dr. Shefali Gokhale, INLAKS and Budhrani Hospital, Pune, India
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Clinical Trials in Hinduja Hospital
17
Typical wholebody image of a patient administered with therapeutic dose (~200 mCi) of 177 LuDOTATATE
Clinical Trials in Hinduja Hospital
18
Typical wholebody image of a patient administered with therapeutic dose (~200 mCi) of 177 LuDOTATATE showing metastic bone lesions
Ga68 DOTANOC SCAN
130mci Lu177 DOTATATE therapy on 18 th August 09 48 hours post therapy whole body scan on 21 st Aug
11 th May 2009
Labeling efficiency was >98%. Only side effect was nausea within 30 minutes after dose administration.
Clinical Trials in Bangalore Institute of Oncology
Conclusions
r An optimized protocol developed for the preparation of injectible 177 LuDOTATATE with adequate specific activity taking into account the variable specific activity of 177 Lu available during the preparation of the agent
r Several batches of the agent were prepared with high radiochemical purity (98.25±1.1%)
r More than 100 patient doses 177 LuDOTATATE prepared following the protocol and has been administered to patients suffering from tumors of neuroendocrine origin
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Acknowledgements
• Radiochemicals Section, Bhabha Atomic Research Centre – Irradiation Planning Group – Radiochemical Processing Group
• Director Radiochemistry and Isotope Group
