User login
Only about 3% to 5% of patients with metastatic colorectal cancer have tumors that are positive for human epidermal growth factor receptor 2 (HER2), and until recently there was no treatment approved by the US Food and Drug Administration (FDA) for this subset of patients.
That all changed, in January of 2023. At that time, the FDA granted accelerated approval to tucatinib (Tukysa) in combination with trastuzumab for RAS wild-type HER2-positive unresectable or metastatic colorectal cancer that has progressed following fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy.
The combination was the first FDA-approved treatment for this patient population.
The only other FDA-approved therapy for metastatic HER2-positive CRC is the antibody-drug conjugate trastuzumab deruxtecan (Enhertu). That drug received accelerated approval from the FDA for metastatic HER2-positive CRC for which no other suitable therapeutic option exists, on April 5, 2024. This FDA action represented an expansion of the drug’s earlier approvals for treating several cancer types, including certain patients with unresectable or metastatic HER2-positive breast cancer and adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who had received a prior trastuzumab-based regimen.
Drug Combo’s Use With Capecitabine in Breast Cancer
Tucatinib is a potent oral tyrosine kinase inhibitor (TKI) that has been shown to be highly selective for HER2. Prior to approval of the colorectal cancer indication, tucatinib had received FDA approval (in April 2020) in combination with trastuzumab and capecitabine for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who had received one or more prior anti-HER2-based regimens in the metastatic setting.
In these patients the combination was associated with significant improvements in both progression-free survival (PFS) and overall survival compared with trastuzumab and capecitabine.
Approval for the colorectal cancer indication was based on results of the phase 2 MOUNTAINEER trial, which were published in The Lancet Oncology.
Real-World Setting
Clinical experience with the combination in a real-world setting is still limited due to the relatively uncommon RAS wild-type HER2-positive CRC subtype, so most of what’s known about the efficacy and safety of tucatinib plus trastuzumab comes from clinical trials. But oncologists interviewed for this article emphasized that the tucatinib-trastuzumab combination nonetheless represents a major breakthrough.
“The population of RAS wild-type HER2-positive is small in colorectal cancer, but the benefit of this treatment is really remarkable. With this combination therapy there was a 38% response rate, and there was a very respectable duration of response. So the population is small, but the benefit of the treatment is by no means small,” said Afsaneh Barzi, MD, PhD, a medical oncologist specializing in gastrointestinal cancers at City of Hope in Duarte, California.
Another medical oncologist interviewed for this piece, who treats patients with HER2-positive metastatic CRC, said that the performance of tucatinib in the real-world setting is in keeping with the efficacy seen in clinical trials.
“There is a group of patients who have a very good response to HER2 [targeted] therapy. Often these are patients who have higher degrees of HER2 amplification, and they do not have concomitant other mutations that activate the pathway, such as RAS mutations,” said Kanwal PS Raghav, MD, MBBS, from the University of Texas MD Anderson Cancer Center in Houston.
Why It Works
In an interview, MOUNTAINEER coinvestigator Tanios S. Bekaii-Saab, MD, from the Mayo Clinic Comprehensive Cancer Center in Phoenix, Arizona, explained why dual HER2 blockade with tucatinib and trastuzumab is an important breakthrough for this population.
“HER2 as a target was already well established in breast cancer and in gastric cancer. In colon cancer we had signals [of anti-HER2 efficacy] but these signals were primarily with dual targeted therapy,” he said.
“What’s unique about tucatinib versus neratinib [Nerlynx], lapatinib [Tykerb] and some of the others is that this is a highly selective tyrosine kinase inhibitor, meaning it is potent just against HER2 and has limited activity against other receptors, classically EGFR, which also goes by the name of HER1,” said MOUNTAINEER trial chair John H. Strickler, MD, of Duke Cancer Center in Durham, North Carolina.
“The reason why that’s valuable is that when you inhibit other receptors like HER1 or EGFR, you can cause significant skin rash and other symptoms that can limit tolerability, which limits your ability to give the full dose. With tucatinib you can more completely inhibit HER2 with fewer side effects,” Dr. Strickler said in an interview.
Dr. Raghav noted that the primary adverse events of therapy with tucatinib have been diarrhea and fatigue, and other common side effects include abdominal pain, fever, nausea, rash, and infusion reactions.
Barriers to Treatment
Dr. Barzi pointed out that in the day-to-day practice setting there are two potential barriers to treatment with tucatinib and trastuzumab for patients with HER2-positive colorectal cancer, hurdles that they would not encounter if they were enrolled in clinical trials.
The first barrier is the requirement for HER2 testing, either through immunohistochemistry or fluorescence in situ hybridization.
“The adoption of HER2 testing in colorectal cancer lags behind other molecular testing, such as testing for KRAS or BRAF, so the provider needs to be aware that HER2 positivity is a possibility,” she said.
The second and more difficult-to-surmount barrier is imposed by the healthcare system. Although the combination is included in National Comprehensive Cancer Network guidelines and, therefore, should not be subject to restrictions or denials by insurers, “the challenge is that this is an oral and IV drug combination,” Dr. Barzi said.
While patients in real-world settings receive intravenous drugs such as trastuzumab in treatment centers, the oral drug component, tucatinib, is dispensed by pharmacies, and patients are often required to shell out high copays for such agents.
Dr. Barzi cited as an example the case of one of her patients who was receiving an oral agent — not tucatinib — for treatment of a different type of colorectal cancer.
“He has very good insurance, and after insurance his out-of-pocket cost on a monthly basis to obtain the drug is $275,” she said.
What’s Next
In colorectal cancer the combination of tucatinib and trastuzumab is approved only in the metastatic setting, but it is also being explored as a first-line therapy in combination with the mFOLFOX6 regimen (5-Fluorouracil, leucovorin, and oxaliplatin) in the MOUNTAINEER-03 trial, which is currently recruiting.
MOUNTAINEER was sponsored by Seagen and Merck. Dr. Strickler reported support from Seagen for the Lancet Oncology manuscript; institutional grants, consulting fees, and travel support from Seagen, and similar relationships with other companies. Dr. Bekaii-Saab reported institutional research and consulting fees from various companies, including Merck, personal consulting fees from various companies, and independent monitoring board/scientific advisory board activities. Dr. Raghav disclosed honoraria and an advisory/consulting role for Seagen and others. Dr. Barzi reported no relevant conflicts of interest.
Only about 3% to 5% of patients with metastatic colorectal cancer have tumors that are positive for human epidermal growth factor receptor 2 (HER2), and until recently there was no treatment approved by the US Food and Drug Administration (FDA) for this subset of patients.
That all changed, in January of 2023. At that time, the FDA granted accelerated approval to tucatinib (Tukysa) in combination with trastuzumab for RAS wild-type HER2-positive unresectable or metastatic colorectal cancer that has progressed following fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy.
The combination was the first FDA-approved treatment for this patient population.
The only other FDA-approved therapy for metastatic HER2-positive CRC is the antibody-drug conjugate trastuzumab deruxtecan (Enhertu). That drug received accelerated approval from the FDA for metastatic HER2-positive CRC for which no other suitable therapeutic option exists, on April 5, 2024. This FDA action represented an expansion of the drug’s earlier approvals for treating several cancer types, including certain patients with unresectable or metastatic HER2-positive breast cancer and adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who had received a prior trastuzumab-based regimen.
Drug Combo’s Use With Capecitabine in Breast Cancer
Tucatinib is a potent oral tyrosine kinase inhibitor (TKI) that has been shown to be highly selective for HER2. Prior to approval of the colorectal cancer indication, tucatinib had received FDA approval (in April 2020) in combination with trastuzumab and capecitabine for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who had received one or more prior anti-HER2-based regimens in the metastatic setting.
In these patients the combination was associated with significant improvements in both progression-free survival (PFS) and overall survival compared with trastuzumab and capecitabine.
Approval for the colorectal cancer indication was based on results of the phase 2 MOUNTAINEER trial, which were published in The Lancet Oncology.
Real-World Setting
Clinical experience with the combination in a real-world setting is still limited due to the relatively uncommon RAS wild-type HER2-positive CRC subtype, so most of what’s known about the efficacy and safety of tucatinib plus trastuzumab comes from clinical trials. But oncologists interviewed for this article emphasized that the tucatinib-trastuzumab combination nonetheless represents a major breakthrough.
“The population of RAS wild-type HER2-positive is small in colorectal cancer, but the benefit of this treatment is really remarkable. With this combination therapy there was a 38% response rate, and there was a very respectable duration of response. So the population is small, but the benefit of the treatment is by no means small,” said Afsaneh Barzi, MD, PhD, a medical oncologist specializing in gastrointestinal cancers at City of Hope in Duarte, California.
Another medical oncologist interviewed for this piece, who treats patients with HER2-positive metastatic CRC, said that the performance of tucatinib in the real-world setting is in keeping with the efficacy seen in clinical trials.
“There is a group of patients who have a very good response to HER2 [targeted] therapy. Often these are patients who have higher degrees of HER2 amplification, and they do not have concomitant other mutations that activate the pathway, such as RAS mutations,” said Kanwal PS Raghav, MD, MBBS, from the University of Texas MD Anderson Cancer Center in Houston.
Why It Works
In an interview, MOUNTAINEER coinvestigator Tanios S. Bekaii-Saab, MD, from the Mayo Clinic Comprehensive Cancer Center in Phoenix, Arizona, explained why dual HER2 blockade with tucatinib and trastuzumab is an important breakthrough for this population.
“HER2 as a target was already well established in breast cancer and in gastric cancer. In colon cancer we had signals [of anti-HER2 efficacy] but these signals were primarily with dual targeted therapy,” he said.
“What’s unique about tucatinib versus neratinib [Nerlynx], lapatinib [Tykerb] and some of the others is that this is a highly selective tyrosine kinase inhibitor, meaning it is potent just against HER2 and has limited activity against other receptors, classically EGFR, which also goes by the name of HER1,” said MOUNTAINEER trial chair John H. Strickler, MD, of Duke Cancer Center in Durham, North Carolina.
“The reason why that’s valuable is that when you inhibit other receptors like HER1 or EGFR, you can cause significant skin rash and other symptoms that can limit tolerability, which limits your ability to give the full dose. With tucatinib you can more completely inhibit HER2 with fewer side effects,” Dr. Strickler said in an interview.
Dr. Raghav noted that the primary adverse events of therapy with tucatinib have been diarrhea and fatigue, and other common side effects include abdominal pain, fever, nausea, rash, and infusion reactions.
Barriers to Treatment
Dr. Barzi pointed out that in the day-to-day practice setting there are two potential barriers to treatment with tucatinib and trastuzumab for patients with HER2-positive colorectal cancer, hurdles that they would not encounter if they were enrolled in clinical trials.
The first barrier is the requirement for HER2 testing, either through immunohistochemistry or fluorescence in situ hybridization.
“The adoption of HER2 testing in colorectal cancer lags behind other molecular testing, such as testing for KRAS or BRAF, so the provider needs to be aware that HER2 positivity is a possibility,” she said.
The second and more difficult-to-surmount barrier is imposed by the healthcare system. Although the combination is included in National Comprehensive Cancer Network guidelines and, therefore, should not be subject to restrictions or denials by insurers, “the challenge is that this is an oral and IV drug combination,” Dr. Barzi said.
While patients in real-world settings receive intravenous drugs such as trastuzumab in treatment centers, the oral drug component, tucatinib, is dispensed by pharmacies, and patients are often required to shell out high copays for such agents.
Dr. Barzi cited as an example the case of one of her patients who was receiving an oral agent — not tucatinib — for treatment of a different type of colorectal cancer.
“He has very good insurance, and after insurance his out-of-pocket cost on a monthly basis to obtain the drug is $275,” she said.
What’s Next
In colorectal cancer the combination of tucatinib and trastuzumab is approved only in the metastatic setting, but it is also being explored as a first-line therapy in combination with the mFOLFOX6 regimen (5-Fluorouracil, leucovorin, and oxaliplatin) in the MOUNTAINEER-03 trial, which is currently recruiting.
MOUNTAINEER was sponsored by Seagen and Merck. Dr. Strickler reported support from Seagen for the Lancet Oncology manuscript; institutional grants, consulting fees, and travel support from Seagen, and similar relationships with other companies. Dr. Bekaii-Saab reported institutional research and consulting fees from various companies, including Merck, personal consulting fees from various companies, and independent monitoring board/scientific advisory board activities. Dr. Raghav disclosed honoraria and an advisory/consulting role for Seagen and others. Dr. Barzi reported no relevant conflicts of interest.
Only about 3% to 5% of patients with metastatic colorectal cancer have tumors that are positive for human epidermal growth factor receptor 2 (HER2), and until recently there was no treatment approved by the US Food and Drug Administration (FDA) for this subset of patients.
That all changed, in January of 2023. At that time, the FDA granted accelerated approval to tucatinib (Tukysa) in combination with trastuzumab for RAS wild-type HER2-positive unresectable or metastatic colorectal cancer that has progressed following fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy.
The combination was the first FDA-approved treatment for this patient population.
The only other FDA-approved therapy for metastatic HER2-positive CRC is the antibody-drug conjugate trastuzumab deruxtecan (Enhertu). That drug received accelerated approval from the FDA for metastatic HER2-positive CRC for which no other suitable therapeutic option exists, on April 5, 2024. This FDA action represented an expansion of the drug’s earlier approvals for treating several cancer types, including certain patients with unresectable or metastatic HER2-positive breast cancer and adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who had received a prior trastuzumab-based regimen.
Drug Combo’s Use With Capecitabine in Breast Cancer
Tucatinib is a potent oral tyrosine kinase inhibitor (TKI) that has been shown to be highly selective for HER2. Prior to approval of the colorectal cancer indication, tucatinib had received FDA approval (in April 2020) in combination with trastuzumab and capecitabine for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who had received one or more prior anti-HER2-based regimens in the metastatic setting.
In these patients the combination was associated with significant improvements in both progression-free survival (PFS) and overall survival compared with trastuzumab and capecitabine.
Approval for the colorectal cancer indication was based on results of the phase 2 MOUNTAINEER trial, which were published in The Lancet Oncology.
Real-World Setting
Clinical experience with the combination in a real-world setting is still limited due to the relatively uncommon RAS wild-type HER2-positive CRC subtype, so most of what’s known about the efficacy and safety of tucatinib plus trastuzumab comes from clinical trials. But oncologists interviewed for this article emphasized that the tucatinib-trastuzumab combination nonetheless represents a major breakthrough.
“The population of RAS wild-type HER2-positive is small in colorectal cancer, but the benefit of this treatment is really remarkable. With this combination therapy there was a 38% response rate, and there was a very respectable duration of response. So the population is small, but the benefit of the treatment is by no means small,” said Afsaneh Barzi, MD, PhD, a medical oncologist specializing in gastrointestinal cancers at City of Hope in Duarte, California.
Another medical oncologist interviewed for this piece, who treats patients with HER2-positive metastatic CRC, said that the performance of tucatinib in the real-world setting is in keeping with the efficacy seen in clinical trials.
“There is a group of patients who have a very good response to HER2 [targeted] therapy. Often these are patients who have higher degrees of HER2 amplification, and they do not have concomitant other mutations that activate the pathway, such as RAS mutations,” said Kanwal PS Raghav, MD, MBBS, from the University of Texas MD Anderson Cancer Center in Houston.
Why It Works
In an interview, MOUNTAINEER coinvestigator Tanios S. Bekaii-Saab, MD, from the Mayo Clinic Comprehensive Cancer Center in Phoenix, Arizona, explained why dual HER2 blockade with tucatinib and trastuzumab is an important breakthrough for this population.
“HER2 as a target was already well established in breast cancer and in gastric cancer. In colon cancer we had signals [of anti-HER2 efficacy] but these signals were primarily with dual targeted therapy,” he said.
“What’s unique about tucatinib versus neratinib [Nerlynx], lapatinib [Tykerb] and some of the others is that this is a highly selective tyrosine kinase inhibitor, meaning it is potent just against HER2 and has limited activity against other receptors, classically EGFR, which also goes by the name of HER1,” said MOUNTAINEER trial chair John H. Strickler, MD, of Duke Cancer Center in Durham, North Carolina.
“The reason why that’s valuable is that when you inhibit other receptors like HER1 or EGFR, you can cause significant skin rash and other symptoms that can limit tolerability, which limits your ability to give the full dose. With tucatinib you can more completely inhibit HER2 with fewer side effects,” Dr. Strickler said in an interview.
Dr. Raghav noted that the primary adverse events of therapy with tucatinib have been diarrhea and fatigue, and other common side effects include abdominal pain, fever, nausea, rash, and infusion reactions.
Barriers to Treatment
Dr. Barzi pointed out that in the day-to-day practice setting there are two potential barriers to treatment with tucatinib and trastuzumab for patients with HER2-positive colorectal cancer, hurdles that they would not encounter if they were enrolled in clinical trials.
The first barrier is the requirement for HER2 testing, either through immunohistochemistry or fluorescence in situ hybridization.
“The adoption of HER2 testing in colorectal cancer lags behind other molecular testing, such as testing for KRAS or BRAF, so the provider needs to be aware that HER2 positivity is a possibility,” she said.
The second and more difficult-to-surmount barrier is imposed by the healthcare system. Although the combination is included in National Comprehensive Cancer Network guidelines and, therefore, should not be subject to restrictions or denials by insurers, “the challenge is that this is an oral and IV drug combination,” Dr. Barzi said.
While patients in real-world settings receive intravenous drugs such as trastuzumab in treatment centers, the oral drug component, tucatinib, is dispensed by pharmacies, and patients are often required to shell out high copays for such agents.
Dr. Barzi cited as an example the case of one of her patients who was receiving an oral agent — not tucatinib — for treatment of a different type of colorectal cancer.
“He has very good insurance, and after insurance his out-of-pocket cost on a monthly basis to obtain the drug is $275,” she said.
What’s Next
In colorectal cancer the combination of tucatinib and trastuzumab is approved only in the metastatic setting, but it is also being explored as a first-line therapy in combination with the mFOLFOX6 regimen (5-Fluorouracil, leucovorin, and oxaliplatin) in the MOUNTAINEER-03 trial, which is currently recruiting.
MOUNTAINEER was sponsored by Seagen and Merck. Dr. Strickler reported support from Seagen for the Lancet Oncology manuscript; institutional grants, consulting fees, and travel support from Seagen, and similar relationships with other companies. Dr. Bekaii-Saab reported institutional research and consulting fees from various companies, including Merck, personal consulting fees from various companies, and independent monitoring board/scientific advisory board activities. Dr. Raghav disclosed honoraria and an advisory/consulting role for Seagen and others. Dr. Barzi reported no relevant conflicts of interest.