Clinical trial results for PHESGO vs PERJETA + Herceptin

Understanding how PHESGO was studied

Because PHESGO is just a different way to give existing treatments, the way PHESGO was studied is a little different than other clinical trials.


The main study was a comparison of PHESGO vs IV PERJETA® (pertuzumab) + Herceptin® (trastuzumab).* This clinical study included 500 people with certain types of HER2-positive early breast cancer. Everyone in the study also received chemotherapy as part of a complete treatment regimen.

The goal of the study was to find out if there were any differences between PHESGO and PERJETA + Herceptin. This study measured the amount of medicine in the bloodstream, which is commonly done to check that the injection works like the infusion. The study also looked at how safe the drug was and if it worked on the cancer.

In this study, no major difference was seen in the amount of medicine that went into the bloodstream with PHESGO compared to PERJETA + Herceptin. The combined results of the study showed no major difference is expected in how it works.

You can get details around side effects and what you may expect here:

*Some patients in the trial were given Herceptin HYLECTA (trastuzumab and hyaluronidase-oysk) injections instead of Herceptin infusions during treatment after surgery.

In another study, more people preferred PHESGO over PERJETA + Herceptin

160 people with HER2+ early breast cancer were asked questions to find out which treatment they preferred. They were given IV PERJETA + Herceptin + chemotherapy before surgery. After surgery, some were given 3 cycles of IV PERJETA + Herceptin then 3 cycles of PHESGO. Others were given PHESGO first then IV PERJETA + Herceptin. Everyone completed a total of 18 cycles of treatment. Patients were asked which treatment they preferred after they completed 6 cycles.

  • Preferred PHESGO (n=136)
  • Preferred IV PERJETA + Herceptin (n=22)
  • No preference (n=2)

The most common reason people preferred PHESGO was because it took less time in the clinic.

  • The most common reason people preferred IV PERJETA + Herceptin was because it felt more comfortable during administration
Have questions?

Call the Patient Resource Center for answers to your questions about PHESGO or other resources from Genentech.

1 (877) GENENTECH (1-877-436-3683)

Monday-Friday, 6am-5pm PST

This is not meant to replace the advice of your healthcare team.

Important Safety Information & Uses

What does PHESGO treat?

PHESGO® (pertuzumab, trastuzumab, and hyaluronidase-zzxf) is a prescription medicine approved for use in combination with chemotherapy for:

  • use prior to surgery (neoadjuvant treatment) in adults with HER2-positive, locally advanced, inflammatory, or early stage breast cancer (tumor is greater than 2 cm in diameter or node-positive). PHESGO should be used as part of a complete treatment regimen for early breast cancer. 
  • use after surgery (adjuvant treatment) in adults with HER2-positive early breast cancer that has a high likelihood of coming back.

PHESGO is a prescription medicine approved for use in combination with docetaxel in adults who have HER2-positive breast cancer that has spread to different parts of the body (metastatic) and who have not received anti-HER2 therapy or chemotherapy for metastatic breast cancer.

What are the most serious side effects of PHESGO?

PHESGO may cause heart problems, including those without symptoms (such as reduced heart function) and those with symptoms (such as congestive heart failure).

  • The risk for and seriousness of these heart problems are highest in people who received both PHESGO and a certain type of chemotherapy (anthracycline)
  • Your doctor will check for signs of heart problems before, during, and after treatment with PHESGO. Based on test results, your doctor may hold or discontinue treatment with PHESGO
  • Contact a healthcare professional immediately for any of the following: new onset or worsening shortness of breath, cough, swelling of the ankles/legs, swelling of the face, palpitations, weight gain of more than 5 pounds in 24 hours, dizziness or loss of consciousness

Receiving PHESGO during pregnancy can result in the death of an unborn baby and birth defects.

  • Birth control should be used while receiving PHESGO and for 7 months after your last dose of PHESGO. If you are a mother who is breastfeeding, you should talk with your doctor about either stopping breastfeeding or stopping PHESGO
  • If you think you may be pregnant, you should contact your healthcare provider immediately
  • If you are exposed to PHESGO during pregnancy, or become pregnant while receiving PHESGO or within 7 months following the last dose of PHESGO, you are encouraged to report PHESGO exposure to Genentech at 1-888-835-2555

PHESGO may cause serious lung problems.

  • Your doctor may check for signs of lung problems including:
    • Severe shortness of breath
    • Fluid in or around the lungs
    • Weakening of the valve between the heart and the lungs
    • Not enough oxygen in the body
    • Swelling of the lungs
    • Scarring of the lungs

Who should not receive PHESGO?

  • PHESGO should not be used in patients who are allergic to pertuzumab, trastuzumab, hyaluronidase, or to any of the ingredients in PHESGO

What are other possible serious side effects?

  • PHESGO may worsen low white blood cell counts caused by chemotherapy: Low white blood cell counts can be life threatening and were seen more often in patients receiving Herceptin® (trastuzumab) plus chemotherapy than in patients receiving chemotherapy alone. Your doctor may check for signs of low white blood cell counts when he or she examines you
  • PHESGO may cause administration-related reactions: PHESGO is given as an injection. The active ingredients in PHESGO have been associated with severe administration reactions, including hypersensitivity or anaphylaxis, which can be fatal. Talk to your doctor if you feel any symptoms. The most common symptoms include dizziness, nausea, chills, fever, vomiting, diarrhea, hives, swelling of the skin, breathing problems, or chest pain

What are the most common side effects?

The most common side effects of PHESGO when given with chemotherapy as part of an early breast cancer regimen are:

  • Hair Loss
  • Nausea
  • Diarrhea
  • Low levels of red blood cells
  • Weakness

The most common side effects of PHESGO when given with docetaxel for treatment of breast cancer that has spread to other parts of the body (metastatic) are:

  • Diarrhea
  • Hair loss
  • Low levels of white blood cells with or without fever
  • Nausea
  • Feeling tired
  • Rash
  • Damage to the nerves (numbness, tingling, pain in hands/feet)

What should I know about side effects with PHESGO?

  • Not all people have serious side effects; however, side effects with PHESGO therapy are common. It is important to know what side effects may happen and what symptoms you should watch for
  • Your doctor may stop treatment if serious side effects happen. Be sure to contact your healthcare team right away if you have questions or are worried about any side effects

You are encouraged to report side effects to Genentech and the FDA. You may report side effects to the FDA at 1-800-FDA-1088 or You may also report side effects to Genentech at 1-888-835-2555.

Talk to a healthcare professional for more information about the benefits and risks of PHESGO. 

Please see full Prescribing Information for additional Important Safety Information, including most serious side effects.

If you cannot afford your medication, visit for financial assistance information.