“Liquid Brachytherapy” Direct Administration of Therapeutic Radioisotopes Into Tumors

1. “Liquid Brachytherapy”Direct Administration of Therapeutic Radioisotopes Into Tumors Jim Simon,*1 Stan Stearns,2 Kenneth McMillan,1 Max Loy,2 and Keith Frank1 IsoTherapeutics Group LLC, Angleton, Texas (1) & Valco Instruments Co. Inc., Houston, Texas (2)

2. 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 if non-target tissue Background Therapy Using Isotopes

3. OpportunityLiquid Brachytherapy • “Brachyceutical” (brachytherapy + radiopharmaceutical) • No encapsulation for radiation to penetrate • Can use particle emitters (β or α) • More precise placement of dose • Fewer side effects

4. Beta-Emitting Isotopes

5. Methods • 177Lu, 153Sm, and 166Ho 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

6. Results • We have found microsyringes, miniature drills and low volume pumps were easy to use and capable of delivering isotopes accurately even when penetrating bone. • High pH formulations were retained at the sites of injection with little migration of the isotope for up to 14 days. • Low pH formulations showed rapid redistribution of the isotope outside the injection site. • In bone, stable chelates were less retained at the site of injection than weak chelates. • HT-29 tumors-bearing mice injected with high pH formulations showed a reduction of tumor growth compared to controls. • Initial results in canine OS show positive clinical effect.

7. Used miniature drill Forms of the Isotope (166Ho): Acidic solution (0.1-0.05 M HCl) Chelated EDTMP complex (labile complex with high chelant concentration) DOTMP complex (inert complex with low chelant concentration) High pH (metal oxide/ hydroxide mixture) 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 High pH formulation remains at injection site Bone Experiments 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 166Ho solution, add 8 µL of water and 2 µL of 50% NaOH

10. Human Xenograft Experiments • Athymic nude mice with HT-29 human colon cancer cell • Tumor size ranged from 64-324 mm3 • 177Lu from MURR (1.09 Ci/mL) in 0.05 M HCl • Low pH formulation is 50:50 solution of 177Lu and 0.05 M HCl • High pH formulation was prepared using 10 µL of 177Lu, 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 177Lu in about 3 µL • One injection in the center of the tumor tumor 7 days Note systemic activity

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

13. Whole Body Retention (Mouse 459)

14. Body Weight 177Lu Injection on Day 1

15. Tumor Size Euthanized Lu-177 Injection on Day 1

16. Summary of Xenograft Data

17. 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

18. How Much Activity is Needed Assume 10,000 rads to ablate tissue (rad = cGy)

19. Dose Comparison • Typical dose of Quadramet is 1 mCi/kg (palliative) • For a 70 kg person that is 70 mCi of 153Sm • For a 1 gram tumor, the dose could be as low as 200 µCi • 70/0.2 = 350 times the dose for new brachyceuticals (resolve tumor)

20. Possible Applications of Technology • Primary Bone Cancer • can replace amputation • Brain Cancer • Prostate Cancer • Replacing seeds • Lung cancers • Many Inoperable Cancers

21. Canine Osteosarcoma Trial • University of Missouri – Columbia • Dept of Veterinary Medicine and Surgery

22. Status of Canine OS Trial • Trial currently in progress • Preliminary results positive • Pain relief • Use of leg First patient

23. 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) • Efficacy demonstrated in dogs (osteosarcoma) • System being developed includes: • Drill to access bone tumors • Pump to deliver sub-microliter amounts

24. 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, brain, pancreatic, prostate, and inoperable tumors. • PCT patent application filed