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For Women With Heavily-Treated Triple-Negative or HR+, HER2- Metastatic Breast Cancer, Padvec Shows Some Anti-Tumor Activity

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June 19, 2024

There may be another new treatment option for women living with metastatic triple negative breast cancer. A promising new study presented at this year’s American Society of Clinical Oncology (ASCO) conference indicated that Enfortumab vedotin (brand name Padcev)  may help women who haven’t responded to standard treatments.

However, while the drug showed anti-tumor activity in women with advanced breast cancer who had already tried several treatment approaches, it was not as effective as researchers hoped.

It’s important to note that Padcev is currently approved for use in urothelial cancer — and it is not yet approved for treating breast cancer.

What’s the Data?

The study, the EV-202 phase II clinical trial, tested women who had two different types of advanced breast cancer — hormone receptor-positive (HR+), HER2 negative breast cancer and triple negative breast cancer.

These trial results are disappointing, but perhaps not the final word on Padcev for the treatment of metastatic breast cancer.

The open-label, multicohort, phase II trial, was performed with eligible adults who had locally advanced or metastatic solid tumors and  good performance status (ECOG 0–1). The Breast Cancer Cohort consisted of patients who had:

  • Prior taxanes or anthracyclines
  • ≥1 standard-of-care cytotoxic regimen and ≤2 lines (L) of cytotoxic therapy for metastatic breast cancer
  • Prior PD-1/L1 inhibitor (TNBC) or endocrine treatment (tx) with a CDK4/6 inhibitor (HR+/HER2- BC)

Patients received Padcev intravenously (1.25 mg/kg on days 1, 8, and 15 of each 28-day cycle) until discontinuation criteria (disease progression, unacceptable toxicity) was met.

The study tracked how well the cancer responded to Padcev. The results showed:

  • Seven (15.6%) of the participants with hormone receptor-positive, HER2-negative breast cancer saw some response
  • Eight people (19%) of the the triple-negative breast cancer group had slightly better results

However, these results did not meet the trial goals of 12 out of 40 responders in the hormone receptor-positive group and 10 out of 40 responders in the triple-negative breast cancer group.

The average time without cancer growing or spreading was:

  • 5.4 months for the hormone receptor-positive group
  • 3.5 months for the triple-negative breast cancer group

What are the side effects?

Like any cancer treatment, Padvec can come with side effects, but these can often be managed.

Some noted side effects include:

  • Skin changes, like rashes, dry skin or itching
  • Numbness or tingling in the hands and/or feet (known as peripheral neuropathy)
  • Feeling of constant tiredness (fatigue)
  • Decrease in appetite or taste changes
  • Loss or thinning of scalp and body hair (alopecia)
  • Eye problems such as blurry vision and dryness
  • Upset stomach, nausea or vomiting
  • Diarrhea
  • Low red blood cell count (anemia)
  • Low white blood cell count (leukopenia or neutropenia)

Other less common, but still important to note, side effects included high blood sugar and pneumonitis.