Drug Overview

The medical agent known as Pafolacianine sodium (OTL38) (referred to by its research code OTL38) is a cutting-edge “Smart Drug” used to improve the accuracy of cancer surgeries. It is not a traditional medicine designed to kill cancer cells or cure disease. Instead, it is an advanced fluorescent imaging ligand that acts as a molecular “flashlight.”

During surgery, this agent helps surgeons see cancerous tissue that might otherwise be invisible to the naked eye under normal hospital lighting. Making the cancer glow allows for more precise removal of tumors while sparing healthy surrounding tissue.

Here are the key details about this agent:

Generic Name: Pafolacianine sodium (OTL38).
US Brand Names: Cytalux.
Drug Class: Optical Imaging Agent / Fluorescent Diagnostic Tool.
Route of Administration: Intravenous (IV) infusion.
FDA Approval Status: FDA-approved for use in patients with ovarian cancer (2021) and lung cancer (2022).

What Is It and How Does It Work? (Mechanism of Action)

To understand OTL38, it helps to imagine a key that only fits one specific lock. In this case, the “lock” is a protein found on the surface of many cancer cells, and the “key” is the Pafolacianine sodium (OTL38) molecule.

The Targeted Key (Folate Receptor)

Many aggressive cancer cells, particularly in the ovaries and lungs, have an unusually high number of “doors” on their surface called Folate Receptor Alpha (FRα). Normal healthy cells have very few of these doors. Pafolacianine sodium (OTL38) is designed to specifically seek out and bind to these FRα receptors.

The Molecular Beacon (Near-Infrared Dye)

The OTL38 molecule consists of two main parts:

The Targeting Ligand: A folic acid derivative that acts as a homing device to find the FRα receptor.
The Fluorescent Dye: A near-infrared (NIR) fluorescent tag (S0456).

How It Works During Surgery

Injection: The drug is injected into the patient’s bloodstream several hours before surgery.
Homing: The ligand travels through the body and sticks specifically to the FRα receptors on cancer cells.
Internalization: The cancer cells “swallow” the Pafolacianine sodium (OTL38) molecule, trapping the fluorescent dye inside the tumor.
Fluorescence: During the operation, the surgeon uses a special Near-Infrared imaging system. When this light hits the tumor, the dye reacts and glows brightly. This allows the surgeon to identify small “satellite” tumors or hidden cancer edges that normal vision would miss.

FDA-Approved Clinical Indications

OTL38 is currently approved by the FDA for specific oncological uses where the Folate Receptor is commonly present.

Oncological Uses:

Ovarian Cancer: Used as an aid to identify malignant lesions that are difficult to see or feel during primary or recurrent surgery.
Non-Small Cell Lung Cancer (NSCLC): Used to help locate lung nodules and identify the exact margins of the tumor during surgical resection.

Non-oncological Uses:

There are currently no FDA-approved non-oncological uses for this agent.

Dosage and Administration Protocols

OTL38 is given as a single-dose infusion by a healthcare professional in a hospital setting shortly before the scheduled surgery.

Important Note: If a patient has a known allergy to folic acid or the imaging dye, the doctor may choose an alternative method.

Clinical Efficacy and Research Results

Recent clinical data (2020–2025) highlights how Pafolacianine sodium (OTL38) has changed the success rates of cancer surgeries.

Improving Ovarian Cancer Outcomes

In the Phase 3 clinical trial (known as the Study 006), surgeons used OTL38 to look for extra cancer after they thought they had finished the surgery using traditional methods.

Detection Rate: In approximately 33 percent of patients, OTL38 identified at least one additional cancerous lesion that was not found by standard visual inspection or touch.
Surgical Precision: By finding these hidden cells, surgeons were able to achieve “complete debulking” (removing all visible cancer) more frequently.

Advancements in Lung Cancer

In the ELUCIDATE trial for lung cancer:

Identifying Margins: OTL38 helped identify positive tumor margins or additional nodules in roughly 19 percent of patients.
Tissue Sparing: Because the glow showed exactly where the cancer ended, surgeons were able to save more healthy lung tissue in many cases.

Safety Profile and Side Effects

OTL38 is generally well-tolerated because it is a diagnostic agent used in a very small amount, not a long-term treatment.

Common Side Effects (greater than 10 percent):

Nausea: Some patients feel mild stomach upset during or after the infusion.
Vomiting: Occasionally follows nausea.
Abdominal Pain: Mild cramping or discomfort.

Serious Adverse Events:

Infusion-Related Reactions: While rare, some patients may experience chest pain, shortness of breath, or skin rashes during the infusion.
Hypersensitivity (Allergy): Severe allergic reactions (anaphylaxis) are possible, as with any IV agent.

Black Box Warning:

There is no FDA Black Box Warning for OTL38.

Management Strategies:

Pre-Surgical Monitoring: Vital signs are checked frequently during the 20-minute infusion.
Folate Restriction: Patients are often asked to avoid high-folate supplements (like multivitamins) for 48 hours before surgery to ensure the cancer receptors are “hungry” for the OTL38.
Nausea Relief: Standard anti-nausea medications can be given if a patient feels unwell during the infusion.

Research Areas

While OTL38 is currently focused on lung and ovarian cancers, it is a significant focus in Research Areas involving other FRα-positive tumors.

Scientists are investigating its use in Pituitary Adenomas and Kidney Cancers. Additionally, there is emerging research on combining OTL38 with Immunotherapy. Researchers hope that by using the fluorescent ligand to map exactly where the folate receptors are located, they can better deliver “Smart” immunomodulating drugs directly to the tumor site. In regenerative medicine, imaging ligands are being studied to help distinguish between healthy regenerating tissue and persistent cancer cells during post-operative healing.

Patient Management and Practical Recommendations

To ensure the highest safety and best surgical results, patients must follow specific instructions regarding their diet and preparation.

Pre-treatment Tests to be Performed:

FRα Expression: While not always mandatory, a biopsy may be checked to ensure the tumor has the Folate Receptors that OTL38 targets.
Pregnancy Test: A negative pregnancy test is required for women of childbearing age, as the effects on an unborn baby are not fully known.

Precautions During Treatment:

Avoid Folic Acid: You must stop taking folic acid supplements, multivitamins, or “prenatal” vitamins for at least 48 hours before the infusion. Folic acid in supplements can block the cancer’s “doors,” preventing OTL38 from sticking to the tumor.
Fasting: Follow standard hospital “NPO” (nothing by mouth) instructions for your surgery.

“Do’s and Don’ts” List:

DO inform your doctor if you have a history of allergies to vitamins or dyes.
DO drink plenty of water leading up to the 48-hour “no-supplement” window.
DON’T take any herbal supplements or vitamins on the morning of surgery.
DON’T be alarmed by the word “ligand”—it simply means a molecule that “links” to a target.

Legal Disclaimer

The information provided in this guide is for educational and informational purposes only and does not constitute medical advice. OTL38 (pafolacianine) is a diagnostic imaging agent and should only be used by trained medical professionals during surgical procedures. Always consult with your surgeon or treating oncologist regarding the risks and benefits of using fluorescent imaging during your specific operation.