Astatine-211and Astatinated Radiopharmaceuticals. Ganesan Vaidyanathan Duke University Medical Center Durham, North Carolina, USA

Transcription

1 Astatine-211and Astatinated Radiopharmaceuticals Ganesan Vaidyanathan Duke University Medical Center Durham, North Carolina, USA

2 Range of "- and $-Particles Y-90 β I-131 β Mean range 215 cells 40 cells At-211 α 3 cells 20 µm m tumor cells Y-90 β I-131 β At 211 α

3 Potential Applications of "-Particle Micrometastases Therapy Tumors of Circulation -Lymphoma -Leukemia Compartmental Tumors -Cystic -Ovarian -Neoplastic Meningitis

4 Radiobiological Advantages of Alpha Particles High relative biological effectiveness (RBE) Low oxygen enhancement ratio Absence of dose rate effects Not dependent on cell cycle

5 At-211 α particles LET mean = 99 kev/:m E ave = 6.79 MeV range = :m Imaging: 211 Po X-rays (EC decay; kev) Astatine-211 Decay Scheme 58% EC 211 Po 0.52 s 207 Bi 38 y EC 211 At 100% E α =7.45 MeV 7.2 h 42% E α = 5.87 MeV 207 Pb IT stable

6 Relative Biological Effectiveness vs. LET At RBE Y 131 I LET (kev/µm)

7 Astatine-211 Production Astatinated Monoclonal Antibodies Meta-[ 211 At]Astatobenzylguanidine 5-[ 211 At]Astato-2 -deoxyuridine Astatinated octreotide Analogues

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9 211 At-Internal Target OGrazing angle at 1.5 o using curved target face -increases beam strike length from 2.5 to 10 cm Top/Front Bottom/Back -improves heat transfer

10 At-211 Internal Target Al vs. Cu backing material -yield -background activity -distillation efficiency Target Configuration -yield -still size, yield

11 Argon

12 211 At Internal Target 209 Bi(",2n) 211 At O Beam currents of µa, 28 MeV "- particles, and hr runs O 0.8 ± 0.1 mci/µaah O Maximum to date: 55 µa H 4.0 h = 178 mci O 67 ± 16% distillation yield

13 Astatine-211 Production Astatinated Monoclonal Antibodies Meta-[ 211 At]Astatobenzylguanidine 5-[ 211 At]Astato-2 -deoxyuridine Astatinated octreotide Analogues

14 N-Succinimidyl 3-[ 211 At]Astatobenzoate ([ 211 At]SAB) for mab Labeling O COOH O Br BuLi Bu 3 SnCl COOR SnBu 3 N-Hydroxysuccinimide, DCC O mab NH 2 + ph min COO N O 211 At COO N O 211 At, TBHP COO N O mab NH CO HOAc, CHCl At SnBu At

15 Clinical Batches of Chimeric 81C6 mab labeled with 211 At Using [ 211 At]SAB 17 batches ( mci) [ 211 At]SAB yield: 54 ± 10% (30% EtOAc fraction from Sep-pak) Conjugation yield: 76 ± 10% Radiochemical purity: 96.0 ± 2.5% (Size exclusion HPLC) Immunoreactive fraction: 83.3 ± 5.3% (Lindmo method)

16 Compartmental Administration: Surgically Created Resection Cavity (SCRC)

17 At-211 Labeled Chimeric 81C6: Clinical Protocol O Thyroid blocking with SSKI and Cytomel beginning 48 hr prior to therapy O Dose administration via indwelling catheter -Single dose of 10 mg of ch81c6 -Escalating doses of 211 At {2 (n=5), 4 (n=6), 6.7 (n=5), and 10 mci (n=1)} O Blood sampling at 1, 2, 4, 8, 12, 18 and 24 hr O SPECT of head and whole body imaging at 2, 4, 8, 18 and 24 hr

18 Patient Characteristics Characteristic Number (%) Median Age (years) 50 Range Gender Male 6 (35%) Female 11 (65%) Karnofsky Performance Score (65%) 90 2 (12%) 80 3 (18%) 70 1 ( 6%) Histology GBM 14 (82%)( AO 3 (18%)

19 Serial whole-body gamma camera images after injection of 211 At-labeled 81C6 in surgical resection cavity % ID Remaining in Cavity (decay corrected ) Location of intracranial cavity 2.2 h 3.8 h 6.2 h 17.4 h Time Post Injection 25.2 h

20 At-211 Activity Distribution in Patients O Median cavity biological clearance half time: 218 hr O Percent decays in cavity: 99.1 ± 0.9% O Blood pool activity (decay corrected): O0.032 ± 0.025% ID at 2 hr O0.26 ± 0.43% ID at 24 hr

21 At-211 Chimeric 81C6: Radiation Dosimetry Tissue Dose (Gy) SRC Margin 1041 Bone Marrow Brain Liver Spleen 0.016

22 211 At Phase I 211 At-labeled Chimeric 81C6: Outcome 1.0 Survival Fraction Median Survival: 54 weeks Weeks Post Therapy

23 N-Succinimidyl 3-[ 211 At]Astato-4- Guanidinomethylbenzoate ([ 211 At]SAGMB) O O COOH COO N COO N Several Steps O 1). 211 At, TBHP O CH 3 I SnBu 3 NBoc HOAc, CHCl 3 2). TFA 211 At NH N NH 2 Boc N H NH 2 Radiochemical yield: 61.7 ± 13.1% L8A4 (anti-egfr viii mab) conjugation yield: 36.1 ± 1.9% Immunoreactive Fraction: 65.2 ± 1.5%

24 In vitro internalization by U87MGEGFR Glioblastoma Cells: L8A4-[ 211 At]SAGMB vs. [ 131 I]L8A4 (Iodogen and [ 131 I]SGMIB) 30 Internalized (%) Time (Hours)

25 Paired-label Tumor Uptake of [ 131 I]SGMIB-L8A4 and [ 211 At]SAGMB- L8A4 in U87MG)EGFR Xenografts %ID per gram At-211 I-131 * * * * Time (hours)

26 211 At/ 131 I Uptake Ratios [ 211 At]SAGMB/[ 131 I]SGMIB L8A4-U87MG)EGFR SPLEEN LUNGS STOMACH [ 211 At]SAPC/[ 131 I]SIPC L8A4-U87MG)EGFR Time (Hours) [ 211 At]SAB/[[ 131 I]SIB 81C6-D54MG Relative 211 At/ 131 I selectivity over 24 h: Lung 5-9; Spleen 5-17; Stomach 1-3

27 Astatine-211 Production Astatinated Monoclonal Antibodies Meta-[ 211 At]Astatobenzylguanidine 5-[ 211 At]Astato-2 -deoxyuridine Astatinated octreotide Analogues

28 Meta-[ 211 At]Astatobenzylguanidine ([ 211 At]MABG) H N NH 2 CH 3 NH Meta-Iodobenzylguanidine (MIBG) I Br Several steps H N NH NH At, NCS TFA, 70 o C H N NH NH At RCY = 85% SiMe 3 Meta-[ 211 At]Astatobenzylguanidine ([ 211 At]MABG

29 [ 211 At]MABG Uptake in SK-N-SH neuroblastoma cells in vitro and tissue distribution in mice in vivo very similar to MIBG Minimal in vivo dehalogenation Exquisite cytotoxicity (more than fold compared to n.c.a. [ 131 I]MIBG and equivalent to only a few 211 At decays per cell in monolayers and multi-cellular spheroids)

30 Gene Therapy plus Targeted "- Particle Radiotherapy Hypothesis Alpha particle emitting compounds can be targeted to tumors via gene expressed markers, and effectively compensate for the heterogeneous nature of gene therapy via Bystander Effect

31 MABG and Gene Therapy htert hterc NET

32 [ 211 At]MABG and Gene Therapy: Uptake in Glioma cells transfected with NET Gene Under the Control of Various Promoters Uptake (CPM/10 5 Cells) 3e+4 3e+4 2e+4 2e+4 1e+4 5e+3 MIBG +DMI MIBG MABG MABG + DMI 0 UVW UVW/ RSV/ NET UVW/ htr/ NET UVW/ htert/ NET

33 [ 211 At]MABG and Gene Therapy: Clonogenic Survival of UVW Spheroids: 100% Cells Transfected with NET A 1 B 1 surviving fraction surviving fraction [ 131 I]MIBG activity concentration (MBq/ml) [ 211 At]MABG activity concentration (MBq/ml) UVW RSV/NET htert/net htr/net

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35 Solid-phase synthesis of [ 211 At]MABG NH P Bu Sn N H NH 2 Bu 211 At, H 2 O 2, HOAc, MeOH NH 211 At N H NH 2

36 [ 211 At]MABG from Polymersupported Precursor: Radiochemical yield vs time Resin: 5 mg Yield (%) Time (Minutes) 211 At: µCi in 50 µl MeOH H 2 O 2 (30%):HOAc 17:10 (v/v): 10 µl Room temp.

37 [ 211 At]MABG: Production at Higher Levels by A Kit Method 10 mg resin mci or 211 At in ~100 µl MeOH 20 µl of H 2 O 2 /HOAc mixture 10 RT Purification by C18 solid-phase extraction Radiochemical yield: 56.4 ± 9.8% (n = 5) Maximum [ 211 At]MABG produced: 5 mci

38 HPLC of [ 211 At]MABG from Kit Method CPM 4e+5 3e+5 2e+5 t R same as of MIBG standard No UV peaks detected 1e Time (Minutes) Waters X-Terra RP18 (4.6 H 250 mm; 5µ) column 0.1%TFA in 20/80 CH 3 CN/Water; 1 ml/min

39 Astatine-211 Production Astatinated Monoclonal Antibodies Meta-[ 211 At]Astatobenzylguanidine 5-[ 211 At]Astato-2 -deoxyuridine Astatinated octreotide Analogues

40 AUdR O HN I (Me 3 Sn) 2, (Ph 3 P) 2 PdCl 2 HO O O N Dioxane O OH 5-Iodo-2'-deoxyuridine (IUdR) O HN 211 At HO HN O O N SnMe 3 HO O O N 211 At, H 2 O 2, HOAc, OH OH 5-[ 211 At]Astato-2'-deoxyuridine CHCl 3, Sonication 20 sec RCY = 85-90%; Max produced: 2.7 mci

41 [ 211 At]AUdR: Rationale µ m heavy recoil damage zone 1 about 120 µ m α -damage zone 2 Two potential zones of high-let kill: 1) a-recoil nuclei (range <0.1 µm) for cells in S- phase taking up AUdR 2) "-particles (range µm) for killing of non S-phase cells by cross fire

42 2 Uptake of [ 211 At]AUdR and [ 131 I]IUdR in D-247 MG human glioma cells Cellular Uptake (mbq/cell) [ 211 At]AUdR [ 211 At]AUdR + 10 µm IUdR [ 131 I]IUdR [ 131 I]IUdR + 10 µm IUdR Blocking with excess IUdR demonstrates saturability of uptake Activity Concentration (kbq/ml) 60

43 Radiotherapy with [ 211 At]AUdR in Rat Neoplastic Meningitis Models - Experiment 1: 43 mci AUdR D341 Med human medulloblastoma 45 mci free [ 211 At]astatide or saline - Experiment 2: A431p human epidermoid carcinoma - Experiment 3: D341 Med human medulloblastoma 28 mci AUdR 61 mci AUdR or saline 3 H 30 mci AUdR 3 H 57 mci AUdR or 3 H saline 1 injection daily for 3 days

44 Results: Experiment 1 Median Survival saline 18 d [ 211 At]astatide 20 d (p=0.56) AUdR 21.5 d (p=0.02) (p=0.07) g v in u rvi a l s s m n i a ge a n t e P erc Saline AUdR 43 µci Time (days) [ 211 At]astatide 45 µci

45 Results: Experiment 2 Median Survival saline 10 d AUdR (28 mci) 17 d (p=0.01) AUdR (61 mci) 16 d (p=0.004) (p=0.7) g n v rv i a ls u m A ni ge a n t e P erc Saline AUdR 61 µci AUdR 28 µci Time (days)

46 Results: Experiment 3 Median Survival saline (3H) 22 d AUdR (3H 30 mci) 27 d (p=0.02) AUdR (3H 57 mci) 31 d (p=0.08) (p=0.49) g v in u rvi a l s s m n i a ge a n t e P erc Saline AUdR 3 x 57 µci AUdR 3 x 30 µci Time (days)

47 AUdR-Summary Intrathecal administration of [ 211 At]AUdR significantly improved the median survival of athymic rats with medulloblastoma neoplastic meningitis The therapeutic efficacy of [ 211 At]AUdR was specific and could be increased by multiple dose protocols There was no evidence of toxicity either in intact animals or on histopathological analysis of the neuroaxis

48 Astatine-211 Production Astatinated Monoclonal Antibodies Meta-[ 211 At]Astatobenzylguanidine 5-[ 211 At]Astato-2 -deoxyuridine Astatinated octreotide Analogues

49 NH 2 -(D)Phe-Cys-Phe-(D)Trp Thr(OL)-Cys-Thr-Lys OCTREOTIDE Cannot be radioiodinated directly NH 2 -(D)Phe-Cys-Tyr-(D)Trp Thr(OL)-Cys-Thr-Lys Tyr 3 -OCTREOTIDE Tyrosine residue can be radioiodinated directly; however, unstable in vivo

50 STRUCTURES OF IBO, INO AND ABO X NH-(D)Phe-Cys-Phe-(D)Trp O Thr(OL)-Cys-Thr-Lys Y IODOBENZOYLOCTREOTIDE (IBO): X = I, Y = CH IODONICOTINYLOCTREOTIDE (INO): X = I, Y = N ASTATOBENZOYLOCTREOTIDE (ABO): X = 211 At, Y = CH

51 HO HO HO OH Structures of Octreotide, Glu-TOCA and GMIBO H 2 N S S D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-CH 2 OH Octreotide H N S S D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Cys-Thr-COOH O GluTOCA OC H N S S D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-COOH I NH N H NH 3 N-(4-Guanidinomethyl-3-iodobenzoyl)Phe 1 -Octreotate (GMIBO)

52 Synthesis of the Tin Precursor (Boc- GMTMSBO), [*I]GMIBO and [ 211 At]AGMBO SPPS S S H 2 N D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-COOH Dde N ε -Dde-Lys 5 -Octreotate a X OC N R H S S N D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-COOH NR NH 2 Dde GMIBO b Boc-Dde-GMIBO; X = I, R = Boc Boc-Dde-GMTMSBO: X = SnMe 3, R = Boc OC H S S N D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-COOH X NH c N H NH 3 [*I]GMIBO; X = *I (30-35%) [ 211 At]AGMBO; X = 211 At (15-20%) a = SGMIB; b = i) ethanolamine ii) TFA; c = i) ethanolamine ii) radioiodine or 211 At, TBHP, HOAc, 70 o C

53 Receptor-binding Assay The affinity of GMIBO was determined using the SSTR-expressing AR42 J rat pancreatic carcinoma cell membranes via a coldsaturation assay. The Scatchard analysis of the data yielded a K d value of 4.8 nm B/F K d = / nm B max /- 292 fmole/mg e-104.0e-106.0e-108.0e-101.0e-9 1.2e-9 Specific Bound[M]

54 Paired-label Internalization of [ 131 I]Glu- TOCA and [ 125 I]GMIBO by D341 Med Cells 20 Internalized (%Dose) Time (Minutes) [ I]GMIBO [ 125 I]GMIBO + Octreotide [ 131 I]Glu-TOCA [ 131 I]Glu-TOCA + Octreotide

55 Figure 5. Paired-label Internalization of [ 131 I]GMIBO and [ 211 At]AGMBO by D341 Med Cells 20 Internalized (%Dose) Time (Minutes) [ 211 At]AGMBO [ 211 At]AGMBO + Octreotide [ 131 I]GMIBO [ 131 I]GMIBO + Octreotide

56 Summary O Astatine-211 in quantities sufficient for the synthesis of clinical batches of astatinated radiopharmaceuticals can be produced O Synthesis of a number of astatinated radiopharmaceuticals, some in quantities sufficient for clinical trails have been achieved O Radiolysis may be the biggest issue; split and pool approach may be necessary

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62 Typical Size-exclusion HPLC of 211 At-ch81C6

63 SAB Yield And Immunoreactive Fraction Of Labeled ch81c6 As A Function Of Radiation Dose r 2 = 0.05 r 2 = 0.29

64 At-211 Production If Clinical Rationale 200 µa internal current 90% distillation efficiency 4 h decay during transportation 720 mci vs. 160 mci

65 At-211 Therapy: Future? Assume: 720 mci/run 5 runs/wk H 50 wk/yr 50% radiochemical yield 5-20 mci/patient dose One Cyclotron yields 4,500 to 18,000 patient doses per year Ovarian 22,000 cases/yr Brain 18,000 cases/yr

66 Astatine-211 Needs Research -10 centers -10 mci/center/wk Phase I/II clinical: -25 centers -1 patient/wk -10 mci/dose Clinical: -100 centers -3 patients/wk -10 mci/dose 100 mci 1 cyclotron H 1 run 250 mci 1 cyclotron H 2 runs 3,000 mci 6 cyclotrons H 3 runs

67 Astatine-211 Rationale 7.2 h Half life "-emission with each decay Po K x-rays for imaging Half life compatible with variety of carriers Chemistry amenable to biomolecules Minimal problem with transformation during decay

68 Increasing 211 At Production Design of internal target system Development of bismuth electroplating method Design of induction heating system Design of specialized cyclotron for 211 At production

69 At-211 Internal Target