Preparation of patient doses of 177 Lu DOTA TATE using indigenously produced 177 Lu : The Indian experience

Transcription

1 TECHNICAL MEETING ON THERAPEUTIC RADIOPHARMACEUTICALS NOVEMBER 2009 VIENNA Preparation of patient doses of 177 Lu DOTA TATE using indigenously produced 177 Lu : The Indian experience Tapas Das, Sudipta Chakraborty, Sharmila Banerjee, Meera Venkatesh Radiopharmaceuticals Division Bhabha Atomic Research Centre, Trombay, Mumbai , INDIA E mail: sharmila@barc.gov.in

2 DOTA TATE as the peptide vector for PRRT HOOC HOOC N N N N COOH O (D pheala) NH O H NH (Cys) O (Tyr) H S NH OH The Potential of both DOTA TATE as a vector for PRRT and 177 Lu as an ideal therapeutic radioisotope unravelled COOH S H O H H H 3 C (Thr) HN OH O (Cys) NH H H 3 C OH O H O HN (Thr) H HN (Trp) H HN O (Lys) N H NH 2 OH Thus 177 Lu DOTA TATE was envisaged as an agent

3 Favourable features of DOTA TATE for PRRT Only effective treatment known for neuro endocrine tumors and presently available in a limited number of countries with prohibitively high cost (~$40,000) Somatostatin receptors Over expressed in a variety of cancers Majority of neuroendocrine tumors Neuroblastomas Some medullary carcinomas Some prostate cancer Small cell lung cancer Octreotide analogue for targeting somatostatin receptors High binding affinity with sst 2 and sst 5 DOTA TATE binding with sst 2 is 9 times better than DOTA TOC Retention of receptor binding potential of DOTA TATE postradiolabeling

4 The challenges in preparing 177 Lu DOTA TATE using indigenously produced 177 Lu Production of 177 Lu with required specific activity using our medium flux research reactors 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 Adequate radiochemical purity and stability post preparation Since specific activity of 177 Lu available at the time of preparation of the agent varies considerably The need for an optimized labeling protocol More importantly with respect to the amount of peptide, in order that it can be prepared with high radiochemical purity using minimum amount of DOTA TATE 4

5 This means Minimum amount of Peptide High specific activity Adequate stabilty after preparation Striking a balance between peptide amount and radiochemical stability 5

6 Production of 177 Lu by direct neutron activation Radionuclidic impurity 175 Lu (n,γ) 176m Lu (β, 3.7 h) 176 Hf (stable) E β(max) = 1.2 MeV E γ = 88 kev 1 d cooling post EOB ensures no 176m Lu in 177 Lu 176 Lu (n,γ) 177m Lu (β, d) 177 Hf (stable) E β(max) E γ = 0.2 MeV = 128, 153, 228, 378, 414, 418 kev 177m Lu only possible RN impurity present in 177 Lu

7 Percentage RN purity of the 177 Lu produced by direct neutron activation Radionuclidic purity of the 177 Lu produced depends on Time of irradiation Neutron flux at which irradiation is carried out The average level of radionuclidic impurity burden in 177 Lu due to 177m Lu found to be nci of 177m Lu / 1 mci of 177 Lu ( kbq / 37 MBq) at EOB Radionuclidic purity of 177 Lu achievable is % to % depending upon the irradiation conditions

8 Specific activity vs. irradiation time %Maximum obtainable activity Specific activity of 177 Lu (GBq.mg 1 ) Time of irradiation (in terms of half life) Duration of irradiation (d) Standard activity vs. irradiation time curve Irradiation of enriched Lu 2 O 3 at n.cm 2.s 1

9 Irradiations with 82% enriched target Irradiations (14 batches) with 82% enriched (in 176 Lu) Lu 2 O 3 target Flux to n/cm 2.s Irradiation period 21 days Typical values of specific activities obtained are between GBq/mg (20 40 Ci/mg) Corresponds to 18% 36 % of the maximum achievable specific activity The specific activity of 177 Lu obtained was significantly higher compared to the theoretically calculated value under the irradiation condition

10 Growth of 177 Lu production in India Lu activity produced (in GBq) [1] 2007 [9] 2008 [9] 2009 [10*] Year (Number of batches) *Production upto the month of October is considered for 2009 Steady Growth in Production

11 Formulation of patient dose of 177 Lu DOTA TATE (typically ~ mci, 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 DOTA TATE was subsequently determined considering that DOTA TATE : Lu molar ratio to be 4:1 (previously optimized) Step III. Required volume of DOTA TATE solution (1 mg/ml in deionized 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 DOTA TATE and 177 LuCl 3 solution Step IV. The preparation was then subsequently heated in at 90 ο C for 60 min at ph

12 A typical example For preparation of a 200 mci (7.40GBq) patient dose of 177 Lu DOTA TATE Amount of Lu 8 µg (since sp. act available at this time is 25Ci/mg, 925 GBq/mg) which is equivalent to µm Lu. The molar ratio of DOTA TATE and Lu need to be 4:1 in the preparation The amount of DOTA TATE which will be required in this case will be 260 µg (molecular weight of DOTA TATE is 1436 The concentration of stock solution of DOTA TATE is 1 µg/µl therefore 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 ( ) 3 µl = 1380 µl i.e. ~1.4 ml. Hence, for the actual preparation, 260 µl of DOTA TATE 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.

13 Formulation of patient dose of 177 Lu DOTA TATE Composition of 200 mci patient dose of 177 Lu DOTA TATE for different 177 Lu specific activity 177 Lu specific activity Amount of lutetium* 20 Ci/mg 10.0 µg (0.057 µm) 25 Ci/mg 8.0 µg (0.045 µm) 30 Ci/mg 6.7 µg (0.038 µm) 35 Ci/mg 5.7 µg (0.032 µm) 40 Ci/mg 5.0 µg (0.028 µm) Amount of DOTA TATE# 326 µg (0.228 µm) 260 µg (0.180 µm) 219 µg (0.152 µm) 186 µg (0.128 µm) 163 µg (0.112 µm) *Radioactive concentration 1 mci/µl # Concentration 1 mg/ml in deionized water Volume of 0.1 M NH 4 OAc (ph ~5) Amount of gentisic acid 177 Lu DOTA TATE specific activity 1.6 ml 64 mg 881 mci/µm 1.4 ml 56 mg 1105 mci/µm 1.3 ml 52 mg 1311 mci/µm 1.2 ml 48 mg 1544 mci/µm 1.1 ml 44 mg 1762 mci/µm 13

14 Salient Features 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 The amount of DOTA TATE required to prepare a patient dose of 200 mci (7.40 GBq) varied from µg and a patient dose is typically achieved in a total volume of ml The radiochemical purity of the 177 Lu DOTA TATE complex was determined to be 98.25±1.1% The agent was obtained with a specific activity of Ci/mg ( GBq/mg) or Ci/mMole ( TBq/mMole)

15 Quality Control Methods Lu DOTA TATE 800 % Radioactivity LuCl 3 CPS Migration from point of spotting (cm) Retention time (s) PC using 50% aqueous acetonitrile HPLC using C18 reverse phase column 15

16 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 16

17 Clinical Trials in Hinduja Hospital Typical whole body image of a patient administered with therapeutic dose (~200 mci) of 177 Lu DOTA TATE 17

18 Clinical Trials in Hinduja Hospital Typical whole body image of a patient administered with therapeutic dose (~200 mci) of 177 Lu DOTA TATE showing metastic bone lesions 18

19 Clinical Trials in Bangalore Institute of Oncology Ga 68 DOTANOC SCAN 11 th May mci Lu177 DOTATATE therapy on 18 th August hours post therapy whole body scan on 21 st Aug Labeling efficiency was >98%. Only side effect was nausea within 30 minutes after dose administration.

20 Conclusions An optimized protocol developed for the preparation of injectible 177 Lu DOTA TATE with adequate specific activity taking into account the variable specific activity of 177 Lu available during the preparation of the agent Several batches of the agent were prepared with high radiochemical purity (98.25±1.1%) More than 100 patient doses 177 Lu DOTA TATE prepared following the protocol and has been administered to patients suffering from tumors of neuroendocrine origin 20

21 Acknowledgements Radiochemicals Section, Bhabha Atomic Research Centre Irradiation Planning Group Radiochemical Processing Group Director Radiochemistry and Isotope Group

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