“Liquid Brachytherapy” Direct Administration of Therapeutic Radioisotopes Into Tumors Jim Simon,* 1 Stan Stearns, 2 Kenneth McMillan, 1 Max Loy, 2 and Keith Frank 1 IsoTherapeutics Group LLC, Angleton, Texas (1) & Valco Instruments Co. Inc., Houston, Texas (2)

2 History A dog named Gabriel –Owner Stan Stearns –Primary bone cancer Bone Cancer in Dogs –Very similar to primary bone cancer in kids ITG Employees Developed Therapeutic Bone Agents –Quadramet –STR

3 Background Brachytherapy –Radioactive source placed in or next to a tissue –Encapsulated to ensure activity does not become systemic –Usually gamma / X-Ray emitting radioisotopes due to the need to penetrate the capsule –Range in tissue higher than desirable –“Seeds” can migrate Radiopharmaceutical –Radioactive construct usually administered systemically –Targets tissue or organ Metabolic (e.g. I-131) Bio-targeting (mAbs) Bone targeting (phosphonates) –Uptake in non-target tissue Therapy Using Isotopes

4 Liquid Brachytherapy Opportunity “Brachyceutical” (brachytherapy + radiopharmaceutical) No capsule for radiation to penetrate Can use particle emitters (β or α) More precise placement of dose Fewer side effects

5 Beta-Emitting Isotopes Half LifeBeta Max Tissue Penetration Gamma 166 Ho26.83 hr1.8 MeV0.85 cm 80.6 keV (6%) 153 Sm46.3 hr0.705 MeV 0.32 cm118 keV (30%) 177 Lu6.7 days0.498 MeV0.17 cm 208 keV (11%) 90 Y64 hr2.28 MeV1.1 cm--

6 Methods 177 Lu, 153 Sm, and 166 Ho were deposited in bone, brain, prostate, and soft tissue tumors Administration was accomplished under anesthesia using custom micro syringes, micro drills and a micro pump. Gamma images and dissection data were used to determine the amount of isotope remaining as a function of time and form of the isotope. A clinical trial in canine osteosarcoma has been initiated

7 Bone Experiments Used miniature drill Forms of the Isotope –Acidic solution ( M HCl) –Chelated EDTMP complex (labile complex with high chelant concentration) DOTMP complex (inert complex with low chelant concentration) Results –Metals in acid migrated quickly –EDTMP complexes showed higher retention than DOTMP complexes –DOTMP complexes had less soft tissue activity and more bone activity femur Bone drill prototype

8 Potential Mechanism HCl formulation –Metal is soluble long enough to become systemic leading to soft tissue (liver) uptake Weak Chelate (EDTMP) –Free metal released from complex has some tenacity for the bone after precipitation, but there is enough time available for migration –Liver activity Strong Chelate (DOTMP) –Complex stays intact and migrates from the injection site depositing in all bone

9 Biodistribution after Bone injection % I.D. 2 Hours after Administration 10 µL of 166 Ho solution, add 8 µL of water and 2 µL of 50% NaOH Bone Injection Site Rest of skeleton Liver HCl52852 EDTMP72211 DOTMP7180 OH9211.7

10 Human Xenograft Experiments Athymic nude mice with HT-29 human colon cancer cell Tumor size ranged from mm Lu from MURR (1.09 Ci/mL) in 0.05 M HCl –Low pH formulation is 50:50 solution of 177 Lu and 0.05 M HCl –High pH formulation was prepared using 10 µL of 177 Lu, 8 µL water, 2 µL of 50% NaOH HT-29 xenograft Direct injection Into tumor

11 Low pH Formulation ( Mouse # 458) Injected with 1.08 mCi 177 Lu in about 3 µL One injection in the center of the tumor tumor Note systemic activity

12 High pH formulation (Mouse 459) Two 5 µL injections 177 Lu (0.8 mCi total) into tumor tumor 14 days

13 Whole Body Retention (Mouse 459)

14 Body Weight 177 Lu Injection on Day 1

15 Tumor Size Euthanized Lu-177 Injection on Day 1

16 Summary of Laboratory Work Rat tissues showing long term retention of isotope: –Bone –Prostate –Brain –Lung Human tumor (HT-29) in mice –Long term retention –Indication of efficacy

17 How Much Activity is Needed Calculate a dose of 200 uCi would give over 10,000 rads to a 1 gram tumor Compare that to Quadramet where a person would get 70 mCi 70/0.2 = 350 times less dose than a Quadramet treatment Resolution of lesion in contrast to pain palliation

18 Canine Osteosarcoma Trial University of Missouri – Columbia –Dept of Veterinary Medicine and Surgery

19 Status of Canine OS Trial Trial currently in progress Preliminary results positive –Pain relief –Use of leg –F-18-FDG Scan No mets (Lung) Little to no uptake in primary tumor First patient

20 Summary Direct administration of beta-emitting isotopes to tumors and tissues High pH formulation identified and is easy to prepare Efficacy demonstrated in mice (HT-29 xenografts) Dogs (osteosarcoma) trial underway. System being developed includes: –Drill to access bone tumors –Pump to deliver sub-microliter amounts –Robotic system to deliver dose precisely to tumor –Refining dosimetry

21 Conclusions Rare earth isotopes administered at high pH are retained with minimal loss of isotope from the site of injection. Low amounts of isotope necessary to treat tumor The system developed warrants further investigation for use in treating cancers such as bone.

22 Thank You