Your diagnosis of ulcerative colitis (inflammation of the large intestine causing ulcers) will be confirmed through endoscopy (a procedure using a camera to look inside the intestine) and tissue analysis if this has not been done previously.

Your disease must have been present for at least 3 months before starting the study.

The inflammation must extend at least 15 centimeters from the anal opening, confirmed by the screening endoscopy.

Your disease activity will be assessed using a scoring system that evaluates symptoms such as bowel movements, rectal bleeding, and the appearance of the intestinal lining during endoscopy. Your score must be between 5 and 9 points, with visible bleeding and significant inflammation.

If you are taking corticosteroids (medications that reduce inflammation) by mouth, the dose must be stable for at least 2 weeks before starting the study. The maximum allowed dose is 20 milligrams per day of prednisone or an equivalent amount of similar medications.

You will be assigned to either Part A or Part B of the study. Both parts last 12 weeks initially, but Part B may continue up to 48 weeks.

The assignment will determine the specific treatment approach and assessment methods used during the study.

You will receive one or more of the study medications. The medications used in this study are SPY001-001 and SPY002, which are long-acting antibodies designed to reduce inflammation in ulcerative colitis.

These medications can be given in two ways: subcutaneously (injection under the skin) or intravenously (infusion into a vein).

The specific medication, dosage, frequency, and method of administration will be determined by the study protocol for your assigned group.

If you are in Part A and taking corticosteroids, you will maintain the same dose throughout the 12-week treatment period.

If you are in Part B and taking corticosteroids, you will maintain the same dose through Week 6, then begin gradually reducing the dose starting at Week 6.

At Week 12, your condition will be evaluated to measure the effectiveness of the treatment.

If you are in Part A, the main assessment will focus on changes in histologic disease activity (examination of tissue samples under a microscope to assess inflammation) compared to the beginning of the study.

If you are in Part B, the main assessment will determine whether you have achieved clinical remission (absence or minimal symptoms of the disease).

Additional assessments will include evaluation of intestinal lining appearance through endoscopy, symptom scores, and blood tests to measure drug levels and immune responses to the study medications.

If you are in Part B, the study may continue beyond Week 12 up to Week 48.

During this extended period, additional assessments will be conducted to evaluate long-term effectiveness, including clinical remission status at Week 48.

Continued monitoring of drug levels and immune responses will occur throughout this period.