Kanjinti is classified as immunotherapy, not chemotherapy. Specifically, it is a monoclonal antibody that targets the HER2 protein found on certain breast and stomach cancer cells. It works in a fundamentally different way than traditional chemotherapy drugs, which kill rapidly dividing cells throughout the body without distinguishing between healthy and cancerous tissue. Kanjinti is a biosimilar to Herceptin, meaning it was developed to work identically to the original brand-name drug.
How Kanjinti Differs From Chemotherapy
Traditional chemotherapy is a blunt instrument. It poisons all fast-growing cells, which is why it causes hair loss, nausea, and drops in blood cell counts. Kanjinti takes a targeted approach: it locks onto the HER2 protein on the surface of cancer cells and works through two distinct pathways.
First, it blocks HER2 from sending growth signals into the cell. In cancers that overexpress HER2 (meaning they have far more of this protein than normal), those signals drive the cancer to grow and divide aggressively. By binding to HER2’s outer surface, Kanjinti essentially jams the signal, stalling the cell cycle so tumor cells stop multiplying.
Second, it recruits your own immune system to destroy the cancer. Once Kanjinti attaches to a cancer cell, immune cells called natural killer cells recognize the antibody’s tail end and latch on. This triggers a process where the immune cells release toxic molecules that punch holes in the cancer cell and kill it. This immune-mediated killing is selective: it preferentially targets cells overexpressing HER2 while largely sparing normal cells.
Why It Gets Confused With Chemotherapy
The confusion is understandable because Kanjinti is almost always given alongside actual chemotherapy drugs. For early-stage breast cancer, it is typically combined with conventional agents like paclitaxel, docetaxel, or carboplatin. For metastatic stomach cancer, it is paired with cisplatin and other cytotoxic drugs. When you’re receiving Kanjinti as part of a treatment regimen that includes chemotherapy, the entire experience can feel like “chemo” because the side effects of those other drugs dominate the picture.
Kanjinti can also be used on its own. The FDA has approved it as a single agent for HER2-overexpressing breast cancer in patients who have already been through chemotherapy for metastatic disease. When used alone, its side effect profile looks quite different from what most people associate with chemotherapy. The most common reactions are headache, diarrhea, nausea, and chills. Hair loss is not listed as a common side effect of Kanjinti by itself.
Who Receives Kanjinti
Kanjinti is only appropriate for cancers that overexpress the HER2 protein. Before starting treatment, your cancer will be tested with an FDA-approved companion diagnostic to confirm HER2 status. Roughly 15 to 20 percent of breast cancers are HER2-positive.
The drug is approved for three main situations: adjuvant treatment of HER2-positive breast cancer (after surgery, to reduce the chance of recurrence), first-line treatment of HER2-positive metastatic breast cancer, and metastatic stomach or gastroesophageal junction cancer that overexpresses HER2. If your cancer does not overexpress HER2, Kanjinti will not work for you.
What Treatment Looks Like
Kanjinti is given as an intravenous infusion in a clinic or hospital setting. It cannot be given as a quick injection. The first infusion typically runs about 90 minutes, and if you tolerate it well, subsequent infusions can be shortened to 30 to 90 minutes.
Dosing schedules vary by the type and stage of cancer. During the chemotherapy portion of breast cancer treatment, Kanjinti is often given weekly for 12 to 18 weeks. After that phase, treatment shifts to every three weeks. For metastatic breast cancer, it may continue weekly until the disease progresses. For stomach cancer, infusions happen every three weeks. Treatment duration can range from months in the adjuvant setting to an indefinite period for metastatic disease, as long as the drug is working and side effects remain manageable.
Side Effects to Be Aware Of
The most notable risk specific to Kanjinti is heart damage. The drug can cause congestive heart failure or reduced heart function, and this risk increases significantly when it is combined with certain chemotherapy drugs, particularly anthracyclines like doxorubicin. Your heart function will be monitored throughout treatment, typically with echocardiograms or similar imaging.
When combined with chemotherapy, patients experience higher rates of low white blood cell counts and febrile neutropenia compared to chemotherapy alone. This is important to understand: some of the more severe side effects you may experience during a Kanjinti-containing regimen are driven by the chemotherapy component, not Kanjinti itself. Other common side effects include fever, chills, fatigue, cough, and rash.
Kanjinti’s Relationship to Herceptin
Kanjinti (generic name trastuzumab-anns) is a biosimilar to Herceptin (trastuzumab), which was the original HER2-targeting antibody approved in the late 1990s. A biosimilar is not a generic drug in the traditional sense. Because antibodies are large, complex proteins made by living cells, a biosimilar must go through extensive comparative testing to prove it matches the reference product in structure, function, and clinical outcomes. The FDA reviewed analytical, animal, and clinical data confirming that Kanjinti performs the same as Herceptin. The primary reason Kanjinti exists is to offer a lower-cost alternative, manufactured by Amgen, while delivering the same therapeutic benefit.