Ontruzant

Trastuzumab

Treatment option:

Medically reviewed

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Ontruzant

Quick Facts

Property	Description
Active ingredient	Trastuzumab (Trastuzumab-dttb)
Form	Powder for concentrate for solution for infusion
Pharmacological class	Antineoplastic Agent, Anti-HER2 Agent
Origin	Biologic, Monoclonal Antibody, Biosimilar
Developer / Marketer	Samsung Bioepis / Organon

What Type of Medicine is Ontruzant?

Ontruzant is a sophisticated targeted biologic medicine classified as an antineoplastic agent (a class of drugs used to manage abnormal growths). Its active ingredient is Trastuzumab, which is a complex protein known as a monoclonal antibody.

Ontruzant is specifically approved as a biosimilar product to the reference biologic, Herceptin. This means it is highly similar in structure, function, and clinical performance to the original product, providing an equivalent treatment option. The high degree of similarity in clinical effectiveness and safety has been supported by extensive comparative studies. This distinction ensures that biosimilars work the same way in the body as the original biologic.

Composition and Physical Form

The core component, Trastuzumab, is a humanized immunoglobulin G1 (IgG1) antibody created using recombinant DNA technology. It is supplied as a sterile lyophilized powder in a vial, which is reconstituted and diluted to create a solution for infusion. The required route of administration is intravenous infusion, delivered directly into a vein under medical supervision. The manufacturing process ensures that the biosimilar exhibits a high degree of consistency and quality in its purity and biological activity compared to the original medicine.

General Purpose as a Targeted Anti-HER2 Agent

The general purpose of Ontruzant is to serve as a targeted therapy for conditions where specific cells overexpress the HER2 protein on their surface. As an Anti-HER2 agent, the medicine operates by binding selectively to the HER2 receptor. This action initiates HER2 receptor blockade and signal transduction interruption, which restricts the affected cell’s ability to receive the external signals needed for growth. This molecular strategy helps control the proliferation of cells driven by the HER2 protein.

What side effects are possible with Ontruzant?

Ontruzant: Possible side effects and safety information

The safety profile of Ontruzant is well-documented in regulatory sources, defining the possible adverse reactions by frequency and the physiological systems affected. The most significant safety constraint highlighted in official labeling is the potential for cardiac dysfunction, including the development of Left Ventricular Dysfunction and Congestive Heart Failure (CHF). This risk is specifically documented to be higher in individuals with pre-existing cardiac conditions or a history of treatment with anthracyclines.

Frequency and Organ Systems Affected

Adverse effects are categorized based on their documented occurrence rates. Infusion-Related Reactions (IRRs) are classified as Very Common, and these systemic events, which may include fever, chills, and fatigue, are noted to occur most frequently during the first infusion. Other effects classified as Very Common involve the blood and lymphatic system (e.g., neutropenia), the gastrointestinal system (e.g., diarrhea, nausea), and musculoskeletal tissues (e.g., arthralgia).

Reactions classified as Common include general cardiac dysfunction and temporary changes like hypotension.

Serious Adverse Reactions and Constraints

Beyond cardiac risk, official documents list other serious adverse reactions, categorized as Uncommon or Rare. These include severe Pulmonary Toxicity (such as interstitial pneumonitis) and severe Anaphylactic reactions. Use is generally restricted in individuals with known severe hypersensitivity reactions to the drug or its components, as well as those with uncontrolled or severe pre-existing cardiac failure.

Overdose and Emergency Response

Overdose and When to Seek Help

The official regulatory profile defines the high-exposure event primarily by the manifestation of severe, established toxicities, rather than a unique set of overdose symptoms. These include acute, serious reactions that can occur during or within 24 hours of administration.

Documented Manifestations and Severe Outcomes

Symptoms that may indicate an acute, severe toxicity event include those consistent with a severe infusion reaction, such as sudden fever, chills, dyspnea (shortness of breath), and hypotension (low blood pressure). Such events carry the potential for serious and fatal outcomes, including acute pulmonary toxicity (e.g., acute respiratory distress syndrome) and severe Cardiomyopathy (heart muscle damage) resulting in clinical heart failure.

Required Emergency Actions

Immediate medical attention is required for any signs of severe infusion reaction or acute cardiac/pulmonary distress. The regulatory guidance mandates that the medicine's administration must be interrupted for symptoms like dyspnea and permanently discontinued for anaphylaxis or acute respiratory distress syndrome. Management is defined as symptomatic and supportive treatment, as no specific antidote is specified in official labeling.

Due to the cardiotoxicity risk, cardiac function (LVEF) must be evaluated prior to and monitored during treatment. The risk of severe cardiac failure is noted to be highest when Ontruzant is administered alongside anthracycline-containing chemotherapy regimens.

Therapeutic Uses of Ontruzant

What Ontruzant Treats: Main Uses and Benefits

This medicine is applied in situations involving certain distressing symptoms linked to HER2-positive cancers. The therapeutic focus is on managing the potential for fluctuating manifestations and recurrence risks associated with these tumors. The use is aligned with therapeutic domains involving significant symptom expression for these conditions, including HER2-overexpressing breast cancer and HER2-overexpressing metastatic gastric or gastroesophageal junction adenocarcinoma.

In clinical settings, this targeted therapy is applied in conditions marked by periods of heightened symptoms, including early-stage cancer (often alongside chemotherapy before or after surgery) and for widespread metastatic disease. For patients with early-stage disease, this therapy may assist with managing symptoms that lead to temporary functional strain, which helps maintain a sense of stability. For advanced disease, the therapy contributes to easing the overall symptom load associated with the condition, which supports the patient during difficult episodes.

“The primary benefit is in offering supportive relief that helps ease the overall symptom burden associated with advanced disease.”

Quick Fact: Relief for Symptom Burden

Context	Benefit
Early-stage disease	Assists with managing functional strain.
Metastatic disease	Supports the management of systemic discomfort.

Eligibility and Restrictions for Use

Eligibility Map: Who can and cannot use Ontruzant — official regulatory information

Category	Official Regulatory Status
Populations for whom use is allowed	Adults with HER2-overexpressing tumors confirmed by a validated test.
Populations for whom use is not recommended	Females during pregnancy or lactation; use in the adjuvant setting beyond one year.
Populations for whom use is contraindicated	Known hypersensitivity to any component; severe dyspnea at rest due to advanced malignancy (EMA/Health Canada).

Age-related eligibility rules

Ontruzant is officially indicated for the treatment of adults (18 years). The safety and effectiveness in pediatric patients (under 18 years) have not been established according to regulatory documentation.

Condition-specific eligibility rules

Cardiac Function: Eligibility is conditional on the Left Ventricular Ejection Fraction (LVEF). The medicine must be withheld for a significant absolute LVEF decrease from pre-treatment values (e.g., 16%) or if LVEF drops below institutional limits and 10% from baseline. Symptomatic Congestive Heart Failure (CHF) is grounds for mandatory permanent discontinuation.
Reproductive Status: Due to the risk of Embryo-Fetal Toxicity, females of reproductive potential must use effective contraception during treatment and for a minimum of 7 months after the last dose.

Connection to the overall eligibility profile: Regulatory documents define who can and cannot use the medicine by establishing mandatory criteria (HER2-positive status, adult age), absolute exclusions (hypersensitivity, severe respiratory compromise), and conditional use rules tied to essential physiological status (cardiac function and reproductive status).

What should I know about interactions with other medicines?

Official Interaction Profile: Interactions with other medicines and products

Ontruzant (trastuzumab-dttb) is a targeted biologic medicine, and its interaction profile is primarily governed by pharmacodynamic rather than metabolic mechanisms. Official regulatory information focuses on two main interaction domains: synergistic toxicity and administrative constraints.

Interaction Domain 1: Pharmacodynamic Risk Reinforcement

Category	Officially Documented Status
Interacting Product Class	Anthracyclines (e.g., Doxorubicin, Epirubicin)
Mechanistic Basis	PD Interaction: Risk reinforcement of cardiac toxicity (Cardiomyopathy)
Timing-Based Rule	Avoid anthracycline-based therapy for up to seven months following discontinuation of Ontruzant.

Interaction Domain 2: Restrictions and Administrative Constraints

The medicine must not be substituted for or co-administered with related antibody-drug conjugates, specifically Ado-trastuzumab emtansine or Fam-trastuzumab deruxtecan, due to mandatory regulatory non-interchangeability rules. Additionally, to prevent compatibility issues, Ontruzant must not be mixed with any other medicines or dextrose (glucose) solution during its preparation or infusion. As a large monoclonal antibody, regulatory documents confirm the absence of clinically relevant pharmacokinetic interactions involving CYP enzymes or drug transporters.

Mechanism of Action

Target Recognition and Signal Blockade

Ontruzant (trastuzumab) is an antibody that primarily works by physically blocking the HER2 protein on the surface of cells that overexpress it. By acting as an antagonist, the drug prevents the HER2 receptors from linking up and transmitting strong growth and survival signals into the cell. This action results in the suppression of overactive proliferation pathways (like PI3K/Akt) and promotes cell cycle arrest and apoptosis in HER2-expressing cells.

Immune System Recruitment

The drug also engages the body's innate immune system via a mechanism called Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC). Once Ontruzant binds to the HER2 protein, its tail segment acts to recruit and activate Natural Killer (NK) cells to execute targeted destruction of the HER2-expressing cells. This results in an augmented elimination pathway that contributes to the overall physiological effect.

Downstream Modulation and Pathway Constraint

By suppressing the upstream HER2 signal, the drug modulates multiple downstream survival cascades and promotes the degradation of the HER2 protein itself. The effectiveness of this mechanism is often constrained when cells rely on alternative, non-HER2 signaling pathways or when the HER2 receptor is truncated.

Dosage and Administration Information

Ontruzant is administered exclusively by intravenous infusion (IV) within a specialized clinical setting, such as a hospital or dedicated infusion center. It is supplied as a powder that requires reconstitution and dilution by a healthcare professional using 0.9% Sodium Chloride Injection, and must not be mixed with other solutions.

The therapy follows a defined, body-weight-based dosing schedule, with the amount calculated in milligrams per kilogram (mg/kg). Treatment begins with a higher loading dose, followed by a consistent, lower maintenance dose. Two main schedules are used: a weekly regimen or a three-weekly regimen, depending on the overall treatment plan.

For the three-weekly schedule, the loading dose is 8 mg/kg, followed by 6 mg/kg maintenance doses every three weeks. The initial infusion typically lasts approximately 90 minutes. Subsequent maintenance infusions may be reduced to about 30 minutes if the first session was well tolerated.

Treatment duration is governed by the context of use. For early-stage conditions, the therapy is given for a fixed period of 52 weeks (one year). For advanced or widespread disease, treatment continues until the condition progresses. If a scheduled dose is missed by more than one week, a full re-loading dose must be given immediately before resuming the regular schedule. No routine categorical dose adjustment is specified for older adults, as dosing remains weight-based.

Recent Clinical Evidence

Ontruzant (trastuzumab-dttb) is a biosimilar approved for the treatment of HER2-positive breast cancer and HER2-positive metastatic gastric or gastroesophageal junction adenocarcinoma. Its approval and use are based on clinical evidence establishing its high similarity to the reference product, trastuzumab.

Clinical Comparability and Equivalence

The most substantial clinical data for Ontruzant comes from Phase 3 trials designed to demonstrate therapeutic equivalence with the reference trastuzumab. These randomized, double-blind, parallel-group studies focused on patients with HER2-positive early or locally advanced breast cancer in the neoadjuvant setting (treatment given before surgery).

The primary endpoint for clinical equivalence was the pathological complete response (pCR) rate in the breast and lymph nodes after completion of the neoadjuvant regimen. Studies showed that the pCR rate with Ontruzant was comparable to that of the reference product, falling within the predefined margin of equivalence.

Safety and Tolerability Profiles

Clinical trials have demonstrated that the overall safety and tolerability profiles of Ontruzant are similar to those of the reference product. Investigators tracked the incidence of adverse events (AEs) and treatment-emergent AEs (TEAEs) in both study arms, finding no clinically meaningful differences.

A key focus of monitoring in all trastuzumab clinical trials is cardiac function. The incidence of treatment-related cardiac adverse events, including asymptomatic left ventricular systolic dysfunction (LVEF decline) and congestive heart failure, was similar between the Ontruzant group and the reference product group during the studies. The most common adverse events reported in the breast cancer studies were neutropenia, alopecia, and nausea.

Treatment Settings Examined in Research

Studies have evaluated Ontruzant in multiple settings:

Setting	Regimen Focus
Adjuvant	Following surgery for HER2+ early breast cancer, often in combination with chemotherapy.
Metastatic	First-line treatment, often with paclitaxel, or as a monotherapy after prior chemotherapy.
Neoadjuvant	Before surgery to shrink tumors, typically combined with chemotherapy.

How should Ontruzant be stored and disposed of?

Storage and Disposal Instructions for Ontruzant

The unreconstituted vials of Ontruzant powder must be stored in a refrigerator at a temperature between 2 C and 8 C (36 F to 46 F). The product must be protected from freezing at all times.

Stability After Reconstitution

Storage stability varies based on the diluent used for reconstitution:

With Preservative (BWFI): The solution is stable for up to 28 days when refrigerated at 2 C to 8 C.
Without Preservative (SWFI): The solution must be used immediately or stored for a maximum of 24 hours when refrigerated.

The final diluted infusion solution is stable for no more than 24 hours when stored in the refrigerator.

Handling and Waste

Ontruzant must be kept out of the reach and sight of children. Disposal of any unused or expired product must be carried out according to local regulatory requirements and should not be done through household waste or wastewater systems.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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