The research study is being done to assess the safety and ability of an investigational drug called CYTALUX (pafolacianine) and a special camera system for the detection of cancer in patients undergoing surgical resection for endometrial cancer.

Study participant's medical history (questions about their health) will be reviewed with them before their surgery to ensure they are able to participate in the study.

It is important for study participants to tell their doctor if they are taking vitamins that contain Folic Acid (vitamin B9), or Folic Acid (vitamin B9) supplements. They will need to stop taking these vitamins at least 48 hours before their scheduled infusion. Folic acid can reduce the effectiveness of the CYTALUX (pafolacianine). Certain other medications have not been studied together with CYTALUX (pafolacianine), so it is important for them to tell their doctor about all medicines and supplements they are taking.

Screening Visit (To see if they can take part in the study and will take place no more than 30 days before surgery)

The following will take place during the Screening Visit. These tests could include those that their doctor would do before any major surgery, in which case they may not be repeated for this trial.

• The doctor and/or a member of the doctor's team will ask them about their health, and obtain a list of all medications, including vitamins and over-the-counter medications (medicines obtained without a doctor's prescription), that they are taking.

Study Drug Infusion (Up to 7 days before surgery)

• Study participants will be scheduled to receive the drug being tested, CYTALUX (pafolacianine), any time from 7 days before their surgery up to the day of their surgery. They will receive CYTALUX (pafolacianine) at least one hour before the imaging portion of their surgery.

• Before they receive the study drug, the following will happen:

  • The doctor and/or a member of the doctor's team will ask about their health and obtain a list of all medications including vitamins and over-the-counter (medicines obtained without a doctor's prescription) medicines that they are taking.
  • For patients who are able to have children, a urine pregnancy test will be done.

• The study drug will be given over about 60 minutes through a vein. The dose of CYTALUX (pafolacianine) given will be calculated by their weight.

Surgery Visit

The following activities related to the study will happen on the day of surgery:

• The doctor will look for cancer as they usually do by feeling and looking throughout the peritoneal cavity using white light and will record the findings.
• After this, the doctor will use the special camera system to look for cancer that may light up where the CYTALUX (pafolacianine) has attached and will record the findings. Any cancer that is seen with the use of the special camera system may be the same as what the doctor recorded earlier without the use of the camera system, or there may be additional cancer seen.
• The doctor will then remove the cancer that has been detected, and any areas that they think should be taken out. This removal of the cancer will be done as the doctor would usually do in surgery for endometrial cancer.
• After the doctor has removed the cancer as discussed above, she/he will once again use the camera system to see if there is any cancer left and the findings will be recorded. Any such cancer observed will be removed based on the doctor's judgment.
• The cancer tissue that is removed will be sent to the lab for further testing.
• Any side effects that a participant may have with the use of CYTALUX (pafolacianine) and/or the camera system will be recorded.
• A sample of any cancer that is removed during this study will be sent to the hospital's laboratory for testing to see if it is endometrial cancer, and to see if the cancer has certain receptors on the surface that would cause the drug, CYTALUX (pafolacianine), to attach to the cancer.

Post-operation Visit (Day 28 ± 7 Days)

• About 4 weeks after the surgery, study participants will be contacted via phone by the doctor and/or a member of the doctor's team, or asked to come to the clinic.
• They will be asked about how they are feeling and about all the medications, including vitamins and over-the-counter (medicines obtained without a doctor's prescription) medicines, that they are taking. The findings will be recorded.

Inclusion Criteria:

1. Provision of signed and dated informed consent form
2. Adult subjects 18 years of age and older
3. Primary diagnosis of endometrial cancer
4. Scheduled to undergo surgery for endometrial cancer
5. Ability to understand the requirements of the study and agree to abide by the study restrictions and to return for the required assessments
6. Willingness to stop the use of folate or folic acid supplements at least 48 hours prior to infusion of study drug

Exclusion Criteria:

1. Pregnancy or positive pregnancy test
2. Any medical condition that in the opinion of the investigator could potentially jeopardize the safety of the subject
3. History of anaphylactic reactions to products containing indocyanine green
4. History of allergy to any of the components of CYTALUX
5. Presence of any psychological, familial, sociological condition or geographical challenges potentially hampering compliance with the study protocol or follow-up schedule

Data will be shared without IPD.