Please select the eligibility criteria that correspond to the clinical trial below.
Title: Calcium and Phosphorus Balance and Calcium Kinetics in Patients With Stage 3/4 Chronic Kidney Disease
Brief Summary: The purpose of this study is to gain a better understanding of calcium absorption and metabolism in patients with Chronic Kidney Disease (CKD) using calcium balance and kinetic methods.


Options:
A: Inclusion Criteria:

1. Men or women \> 18 years of age;
2. The subject has voluntarily signed and dated the most recent informed consent form approved by an Institutional Review Board (IRB);
3. The subject will, in the opinion of the investigator, be compliant with prescribed therapy and all study visits;
4. Subject must be able to communicate and be able to understand and comply with the requirements of the study;
5. For subjects not on dialysis estimated GFR at screening \< or equal to 60 ml/min + 10 % that in the opinion of the investigator is stable and not expected to initiate dialysis within 3 months;
6. Subject must have serum phosphorus at screening of greater than or equal to 3.5 mg/dL;
7. Subjects must have a screening salivary flow rate by Saxon test ≥ 1 g/2 min;
8. All subjects must have NO change in prescribed dose or frequency of any of the following medications ≥ 14 days prior to Run-In Visit 2 (Day -15):

a. Phosphate binding products including prescribed and over-the counter b. Oral or injectable active vitamin D c. Oral nutritional vitamin D d. Calcium supplements e. Anti-osteoporotic medication (e.g. bisphosphonates) f. Cinacalcet i. Subject must be prescribed a diet appropriate for patients with their stage of CKD, must be willing to avoid intentional changes in diet and must have stable nutritional status in the opinion of the investigator.

j. Subjects on dialysis must, in the opinion of the investigator, have a stable dialysis prescription, stable dialysis access and a URR \>/= 65% for at least 4 weeks prior to Day -15.

Exclusion Criteria:

1. Subject is receiving or has received an investigational product (or is currently using an investigational device) within 14 days prior to Visit 2 (Day -15);
2. Subject has a known sensitivity to chitin or allergy to shellfish;
3. Subject has had dental work other than cleaning, cavity filling or crown placement within 48 hours prior to Visit 4 (Day 1) or at any time during the course of the trial;
4. Subject has a clinically significant infection requiring treatment with antibiotics (within 7 days prior to Visit 2 (Day -15));
5. Subject has had an inpatient hospitalization within 14 days prior to Visit 2 (Day -15) with the exception of hospitalizations related to vascular access procedures;
6. Subject has a known history of immunodeficiency diseases, including a positive HIV (ELISA and Western blot) test result;
7. Active drug or alcohol dependence or abuse (excluding tobacco use) in the opinion of the principal investigator;
8. In the opinion of the investigator, subject is unable to chew gum for 30 minutes;
9. Subject has an unstable medical condition which in the opinion of the investigator would compromise successful completion of the study;
10. Subject is receiving calcimimetic therapy (acceptable if subject is on dialysis);
11. Subject has known salivary gland dysfunction or Sjogren's syndrome;
12. Subjects is receiving niacin therapy within 7 days prior to Run- In Visit 2(Day -15) (use as part of standard multivitamin is acceptable);
13. Subject has had a major cardiovascular event within 90 days of screening. The investigator should be guided by evidence of any of the following;

a. Acute myocardial infarction b. Acute cerebral vascular event c. Vascular surgical intervention d. Coronary Revascularization e. Decompensated congestive heart failure

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B: Inclusion Criteria:

1. Men or women \> 18 years of age;
2. The subject has voluntarily signed and dated the most recent informed consent form approved by an Institutional Review Board (IRB);
3. The subject will, in the opinion of the investigator, be compliant with prescribed therapy;
4. Subject must be able to communicate and be able to understand and comply with the requirements of the study;
5. For subjects with CKD not on dialysis- kidney function at any stage that in the opinion of the investigator is stable and not expected to initiate dialysis within 3 months;
6. For subjects with CKD not on dialysis- a screening serum phosphorus value greater than or equal to 4.5 mg/dL;
7. For subjects with ESRD - a screening serum phosphorus value greater than or equal to 4.6 mg/dL and less than or equal to 9.0 mg/dL and one of the two conditions: A mean historical value of the most recent 2 phosphorus measurements ≥ 4.6 and less than or equal to 9.0 mg/dL at the time of written informed consent or A second screening serum phosphorus value greater than or equal to 4.6 mg/dL and less than or equal to 9.0 mg/dL performed not less than 7 days from the date of the previous screening;
8. In the opinion of the investigator, subjects with ESRD must be prescribed a stable dialysis regimen (3x/week) for ≥ 4 weeks prior to baseline and must have a stable dialysis access;
9. Subjects with ESRD must have an historical URR ≥ 65% for at least 4 weeks prior to baseline;
10. All subjects must have NO change in prescribed dose or frequency of any of the following medications ≥ 14 days prior to baseline:

    1. Phosphate binding products including prescribed and over-the counter
    2. Oral or injectable active vitamin D
    3. Oral nutritional vitamin D
    4. Calcimimetics
    5. Calcium supplements
    6. Anti-osteoporotic medication (e.g. bisphosphonates)
11. Subject must be prescribed a diet appropriate for patients with their stage of kidney disease, and must be willing to avoid intentional changes in diet; and
12. Subjects must have a screening salivary flow rate by Saxon test ≥ 1 g/2 min.

Exclusion criteria:

1. Receiving or has received an investigational product (or is currently using an investigational device) within 28 days prior to baseline;
2. Known sensitivity to chitin or allergy to shellfish;
3. Clinical evidence of active malignancy and/or receiving systemic chemotherapy/radiotherapy with the exception of basal cell or squamous carcinoma of the skin;
4. Clinically significant infection requiring treatment with antibiotics (within 7 days prior to baseline);
5. Inpatient hospitalization within 14 days prior to baseline with the exception of hospitalizations related to vascular access procedures;
6. Planned surgical intervention for secondary hyperparathyroidism;
7. In the opinion of the investigator, inability to chew gum for 60 minutes;
8. Planned relocation to another area within the next 4 months;
9. Subject has a known history of immunodeficiency diseases, including a positive HIV (ELISA and Western blot) test result;
10. Active drug or alcohol dependence or abuse (excluding tobacco use) in the opinion of the principal investigator;
11. Unstable medical condition which in the opinion of the investigator would compromise successful completion of the study;
12. Known active liver disease with AST or ALT levels greater than 3X the upper limit of normal; and
13. Subject has had a major cardiovascular event within 90 days of screening. The investigator should be guided by evidence of any of the following;

    1. Acute myocardial infarction
    2. Acute cerebral vascular event
    3. Vascular surgical intervention
    4. Coronary Revascularization
    5. Decompensated congestive heart failure
C: Inclusion Criteria:

* age \>18 years
* eGFR 20-45 by modified MDRD equation
* protein/creatinine ratio \<5
* blood pressure \<150/95
* not taking calcium binder or supplements, vitamin D, or phosphate binders
* normal serum phosphorus and calcium corrected for albumin and intact PTH \<100pg/ml
* medically stable
* able to give informed consent and come for all visits

Exclusion Criteria:

* history of significant liver disease or cirrhosis
* medically unstable
* unable to tolerate diets
D: Inclusion Criteria:

1. Patients with a GFR of \< 45 ml/min;
2. Intact serum PTH \> 37 pg/ml;
3. Age \> 35 years (both genders and all races);
4. Able to perform two three-week balance studies;
5. Not on oral calcium or vitamin D other than multi vitamin, or willing to stop calcium or vitamin D for one month prior to entry in the study (day 1 of first calcium balance period);
6. Female patients must be post-menopausal (defined as last menstrual period at least 12 months prior to screening visit) or surgically sterile by hysterectomy;
7. On stable doses of diuretics, bisphosphonates, anti-epileptics (except dilantin) for at least 2 months.

Exclusion Criteria:

1. Serious underlying systemic disease (including uncontrolled diabetes, lupus, hypertension, amyloid, etc);
2. Taking drugs that alter calcium and phosphate balance or homeostasis including high dose cholecalciferol or ergocalciferol (1000 U/day or 50,000U/ wk, respectively), active vitamin D metabolites, calcimimetics, PTH analogues in the last 30 days;
3. Taking drugs that the investigator feels will alter calcium balance;
4. Plan to initiate dialysis in the next six months;
5. Hypercalcemia defined as serum calcium \> 10.5 mg/dl;
6. Hyperphosphatemia defined as serum phosphate \>5.5mg/ml;
7. Intestinal disease that alters absorption or normal intestinal function including celiac disease, small bowel resection, bariatric surgery;
8. Smoking

Answer: D