The primary objective of this study is to determine the safety and tolerability of extended dosing of GCS-100 in patients with CKD.

Galectin-3 contributes to fibrosis, is elevated in patients with ESRD, and correlates with adverse outcomes. Animal models with genetic knockout of galectin-3 demonstrate a reduction in structural and functional deficits in the kidney. GCS-100 is a galectin-3 antagonist that has been shown to reduce fibrosis pre-clinically. Based on the role of galectin-3 and fibrosis in kidney disease, the Sponsor believes GCS-100 may be effective at treating patients with CKD.

Study GCS-100-CS-4002 is an ongoing randomized, placebo controlled study of GCS-100 in Stage 3b and 4 CKD. The objective of the study is to determine the safety and efficacy of 8 weekly injections of GCS-100 on eGFR. Patients who have completed that study without adverse safety events, may be asked to participate in this study to test the safety of prolonged administration of study drug.

Inclusion Criteria:

1. Subject is capable of understanding the purpose and risks of the study and is able to provide written informed consent
2. Subject was enrolled in and completed the End of Study (Day 85) of GCS-100-CS-4002

Exclusion Criteria:

1. Subject experienced a Grade 3 or worse adverse event related to GCS-100 in clinical study GCS-100-CS-4002

2. Systolic blood pressure ≤90 mmHg and ≥160 mmHg and diastolic blood pressure ≤40 mmHg and ≤100 mmHg at screening

3. Subject has clinical laboratory results of:

   1. Hemoglobin: ≤9g/dL
   2. Total bilirubin: >1.5X the upper limit of normal (ULN)
   3. ALT and/or AST: >2.5X ULN

4. Subject has a concomitant disease or condition, including laboratory abnormalities, which, in the opinion of the investigator, could interfere with the conduct of the study or put the subject at unacceptable risk

5. Subject who may require renal replacement therapy within the next 2 months, at the discretion of the investigator