FDA Approves Tukysa Plus Herceptin for HER2-Positive Metastatic Colorectal Cancer

The Food and Drug Administration (FDA) approved Tukysa (tucatinib) plus Herceptin (trastuzumab) for the treatment of patients with previously treated HER2-positive metastatic colorectal cancer, according to a press release from Seagen, the drug’s manufacturer.

“The finding that colorectal cancer overexpress HER2 because of genetic mutations that causes cancer cells to grow now has relevancy in the treatment of colorectal cancer is a bit of a surprise,” Dr. Richard Goldberg, member of the board of directors and medical advisory board at Fight CRC, said in an interview with CURE®. “ This mutation is quite common in breast cancers and now we know that 5-7% of patients with advanced colorectal cancer have this genetic change as a driver of their cancer as well. Drugs designed to target this abnormal growth pathway are now bearing fruit in colorectal cancer treatment as they have in breast cancer.”

The FDA approval is based off findings from the phase 2 MOUNTAINEER trial, which showed that Tukysa plus Herceptin may be an attractive chemotherapy-free regimen for this patient population.

MOUNTAINEER findings showed that at an average follow-up of 20.7 months, 38% of patients given Tukysa plus Herceptin had a confirmed objective response, meaning that their disease shrunk as a result of treatment. Among these patients, average duration of response was 12.4 months.

Additionally, average progression-free survival (time from treatment until disease worsens) was 8.2 months, and average overall survival (time from treatment until death of any cause) was just over two years (24.1 months).

“The study that led to the approval of the drug was done on patients who had a history of previous treatment and had exhausted all other forms of treatment (chemotherapy and targeted therapy drugs), but as this is commonly the case, these kinds of treatments will be found to be more effective as earlier lines of therapy, a strategy which the company is now investigating,” Goldberg said.

However, patients must have their tumors analyzed for genetic mutations before they can be treated with regimens such as Tukysa and Herceptin. Sometimes, that means that patients must advocate for themselves and bring it up to their providers.

“The most important conversation that patients should have with their provider is having their tumors analyzed using one of the many commercial or institutional panels for looking at driver mutations in tumors. Tumor tissue can be analyzed by a number of methods including genetic sequencing. A pathologist can simply use a marker to process a piece of the tumor and determine if the tumor cells overexpress HER2 and, if present, this finding suggests that this pathway is driving their tumor's growth. Unfortunately, not all oncologists do that; it is less common in community practices,” Goldberg said. “I would also say that there is a difference in comfort levels in using these new target therapies among oncologists, so it is important that you talk to your provider about this or ask for a referral for an opinion at an academic cancer center to help determine if this strategy is right for an individual with advanced colorectal cancer.”

Additionally, patients who are prescribed Tukysa plus Herceptin should be aware of potential side effects. The most commonly observed side effects in the trial were diarrhea, fatigue, rash, fever, nausea and infusion-related reaction, as Herceptin is administered intravenously.

“This is just the beginning of the potential benefit for this approach and an additional option for a subset of patients whose tumors tend to have poorer outcomes,” Goldberg said, noting that while this regimen provides an exciting new advancement, it does not cure the disease.

“Until we can cure every patient with advanced disease, we need to continue researching and finding new alternatives,” he said. “This treatment has been tested in a way that cure is not the goal, rather, extension of life is the goal. It is possible that before this subset of patients, earlier application of this approach could have curative outcomes but remains to be tested with ongoing research.”

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