Clonal Emergence and Regression During Radium-223 Therapy for Metastatic Prostate Cancer

This study proposes to document the presence of clonal emergence and regression during
radium-223 therapy for metastatic prostate cancer by serial ctDNA analysis of
tumor-associated mutations, using the clinically-available Guardant 360 platform. These data
may provide important mechanistic insights into radium-223 therapy by 1) identifying
mutations associated with radium-223 resistance or sensitivity, 2) providing new markers of
treatment response in an individual, and 3) revealing antitumor effects from radium-223 that
are not easily recognized with standard tumor response metrics. Positive finding based on
this clinically-available platform will be readily applied by the oncology treatment
community.

INCLUSION CRITERIA

1. Prostate adenocarcinoma by history or medical records.

2. Two or more bone metastases as demonstrated by imaging studies (technetium bone scan,
fluoride PET scan, FDG PET scan, fluciclovine PET scan, CT scan, or MRI scan) or by
biopsy.

3. Patients must be on ADT with a GnRH receptor agonist/antagonist or orchiectomy, with
or without an anti-androgen or testosterone synthesis inhibitor. Patients must have a
documented castrate level of testosterone (<50ng/dL) and be willing to continue their
GnRH agonist/antagonist during the course of radium-223 therapy.

4. Patients may have had localized external beam radiation to as much as 20% of the
skeleton

5. Adequate hematopoietic, renal, and hepatic function. These parameters include:

- Hemoglobin ≥ 10gm/dL

- WBC ≥ 3.0K/mcL

- ANC ≥ 1.5K/mcL

- Platelet count ≥ 100K/mcL

- Creatinine < 1.5 ng/mL

- Total bilirubin <1.5 ng/mL.

- Albumin > 25 g/L

6. Patients should have an elevated, relevant tumor marker such as PSA, CEA, or LDH.

7. Age ≥18 years old

8. Life expectancy of at least 24 weeks

9. Subjects must be able to understand and be willing to sign the written informed
consent form. A signed informed consent form must be appropriately obtained prior to
the conduct of any trial-specific procedures. Subjects must be willing and able to
comply with the protocol, including follow-up visits and examinations.

10. Men of childbearing potential must agree to use adequate contraception beginning at
the signing of the informed consent until at least 30 days after the last dose of
radium-223 treatment or during the course of radium-223 treatment.

11. Subjects must have had a Guardant 360 ctDNA-based genomic profile performed up to four
months prior to the first dose of radium-223, with no new therapy started in the
interim. This assay must show at least one single nucleotide variant, either missense
or synonymous, or one amplification.

12. Subjects should continue any previously-started bone-hardening agents (zoledronic acid
or denosumab) during radium-223 therapy.

13. All acute toxic effects of any prior treatment have resolved to NCI-CTCAE v 5.0 Grade
1 or less at the time of signing the Informed Consent Form (ICF).

EXCLUSION CRITERIA

1. Initiation of any additional anti-tumor therapy within 2 months of starting radium-223
treatment

2. Presence of only lytic bone metastases

3. Prior cytotoxic chemotherapy for metastatic PCa

4. Prior systemic therapy with radionuclides (e.g., strontium-89, samarium-153,
rhenium-186, or rhenium-188, or Radium Ra 223 dichloride) for the treatment of bony
metastases

5. Other malignancy requiring systemic therapy within the last 3 years (except non
melanoma skin cancer or low-grade superficial bladder cancer)

6. Visceral (i.e. liver, lung, brain, adrenal, brain, but not lymph node) metastases as
assessed by chest, abdominal, or pelvic computed tomography, or other imaging
modality)

7. Lymphadenopathy exceeding 6 cm in short-axis diameter, or any size pelvic
lymphadenopathy if it is thought to be a contributor to concurrent hydronephrosis

8. Imminent spinal cord compression based on clinical findings and/or MRI. Treatment
should be completed for spinal cord compression.

9. Any infection ≥ Grade 2 per NCI-CTCAE version 5.0

10. Cardiac failure NYHA III or IV

11. Crohn's disease or ulcerative colitis

12. Bone marrow dysplasia, myelodysplasia

13. Fecal incontinence

14. Inability to comply with the protocol and/or not willing or not available for
follow-up assessments.

15. Any condition which, in the investigator's opinion, makes the subject unsuitable for
trial participation.

16. Concurrent use of abiraterone or enzalutamide. A 28-day washout period is required for
both agents.