The oral kinase inhibitor tucatinib (Tukysa – Seagen) has received accelerated approval from the FDA for use in combination with trastuzumab (Herceptin) for treatment of adults with RAS wild-type human epidermal growth factor receptor 2 (HER2)-positive unresectable or metastatic colorectal cancer that has progressed following treatment with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy regimens. Tucatinib was approved in 2020 for use in combination with trastuzumab and capecitabine (Xeloda, and generics) for treatment of adults with advanced unresectable or metastatic HER2-positive breast cancer, including those with brain metastases, who received at least one prior anti-HER2-based regimen for metastatic disease.

The oral tyrosine kinase inhibitor neratinib (Nerlynx – Puma Biotechnology) has been approved by the FDA for use in combination with capecitabine (Xeloda, and generics) for treatment of advanced or metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer in adults who received ≥2 prior anti-HER2-based regimens for metastatic disease. It was previously approved for use as monotherapy for extended adjuvant treatment of adults with early-stage, HER2-positive breast cancer following adjuvant trastuzumab (Herceptin)-based therapy. HER2 is overexpressed in about 20% of breast cancers. Up to 30% of early-stage, HER2-positive breast cancer cases treated with trastuzumab-based adjuvant therapy recur. Neratinib is the only HER2-directed small molecule approved for treatment of early-stage and metastatic HER2-postive breast cancer.

The FDA has approved two new drugs for treatment of previously-treated unresectable or metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer: fam-trastuzumab deruxtecannxki (Enhertu – Daiichi-Sankyo/AstraZeneca), an IV HER2-directed monoclonal antibody linked to the topoisomerase I inhibitor DXd, and tucatinib (Tukysa – Seagen), an oral tyrosine kinase inhibitor.

The FDA has approved the pyrimidine analog uridine triacetate (Vistogard – Wellstat Therapeutics) for emergency treatment of a fluorouracil (5-FU) or capecitabine (Xeloda, and generics) overdose or severe toxicity that occurs within 96 hours following administration of one of these drugs. Fluorouracil is a cytotoxic antimetabolite used to treat breast, colorectal, and other cancers; capecitabine is an oral prodrug of fluorouracil.

Uridine triacetate, a prodrug, is deacetylated to uridine after oral administration. Excess circulating uridine is converted into uridine triphosphate, which inhibits the cytotoxic activity of 5-fluorouridine triphosphate, a fluorouracil metabolite, by competing with it for incorporation into RNA.

FDA approval was based on two unpublished open-label studies (summarized in the package insert) in a total of 135 adults and children with overdoses of fluorouracil or capecitabine (n=117) or severe or life-threatening toxicities within 96 hours after their administration (n=18). The overall survival rate at 30 days was 96%. In retrospective case reports that included 25 patients who received only supportive care after a fluorouracil overdose, the survival rate was 16%.

Vistogard is supplied as orange-flavored oral granules in single-dose packets containing 10 grams of uridine triacetate. The granules should be mixed with 3-4 ounces of soft food and taken every 6 hours for 20 doses. The recommended dose is 10 grams for adults and 6.2 grams/m² (10 grams maximum) for children. Mild to moderate nausea, vomiting, and diarrhea have been reported. The cost for one course of treatment is $75,000.1

1. Approximate WAC. WAC = wholesaler acquisition cost or manufacturer's published price to wholesalers; WAC represents a published catalogue or list price and may not represent an actual transactional price. Source: AnalySource® Monthly. June 5, 2016. Reprinted with permission by First Databank, Inc. All rights reserved. ©2016. www.fdbhealth.com/policies/drug-pricing-policy.

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The FDA has approved the pyrimidine analog uridine triacetate (Xuriden [zur' uh den] – Wellstat Therapeutics) for treatment of hereditary orotic aciduria, a rare autosomal recessive disorder (estimated birth prevalence: <1:1,000,000) in infants and children caused by a deficiency in uridine 5'-monophosphate (UMP) synthase. This deficiency prevents synthesis of uridine nucleotides and causes developmental delays, failure to gain weight, hematologic abnormalities, and excessive urinary excretion of orotic acid, which can lead to urinary obstruction.1 Xuriden is the first drug to be approved in the US for this indication. Uridine triacetate is also available as Vistogard for treatment of fluorouracil (5-FU) or capecitabine (Xeloda, and generics) overdose or severe or life-threatening toxicity.

In an unpublished, single-arm, 6-week trial with a 6-month extension (summarized in the package insert), 4 patients 3-19 years old with hereditary orotic aciduria were treated with uridine triacetate 60 mg/kg once daily for 6 weeks, followed by 60-120 mg/kg once daily for 6 months. After 6 months of treatment, hematologic parameters (neutrophil count, WBC count, or mean corpuscular volume) either improved or remained stable and orotic acid levels remained stable in all 4 patients. Weight growth either improved or remained stable and height growth remained stable in 3 patients measured after 6 months of treatment. No adverse effects were reported.

Xuriden is available as oral granules in 2-gram single-use packets. The recommended starting dosage is 60 mg/kg once daily. The dose can be increased to 120 mg/kg (max 8 grams) once daily if urine orotic acid levels increase or remain above normal, or for worsening disease. The granules should be mixed in applesauce, pudding, yogurt, milk, or infant formula and swallowed immediately, without chewing. Once the packet is opened, any unused granules should be discarded. The cost for 30 2-gram packets of Xuriden is $22,500.2

1. S Balasubramaniam et al. Inborn errors of pyrimidine metabolism: clinical update and therapy. J Inherit Metab Dis 2014: 37:687.
2. Approximate WAC = wholesaler acquisition cost, or manufacturer's published price to wholesalers; WAC represents published catalogue or list prices and may not represent an actual transactional price. Source: AnalySource® Monthly. March 5, 2016. Reprinted with permission by First Databank, Inc. All rights reserved. ©2016. www.fdbhealth.com/policies/drug-pricing-policy.

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Ado-trastuzumab emtansine (Kadcyla – Genentech), a human epidermal growth factor receptor 2 (HER2)-targeted antibody and microtubule inhibitor conjugate, has been approved by the FDA for intravenous (IV) treatment of HER2-positive metastatic breast cancer in patients previously treated with trastuzumab (Herceptin) and a taxane. The prefix was added to the new conjugate’s name at the request of the FDA to distinguish it from trastuzumab.

Eribulin mesylate (Halaven – Eisai) has been approved by the FDA for treatment of patients with metastatic breast cancer who have previously received at least 2 chemotherapy regimens for metastatic cancer. Prior therapy should have included an anthracycline and a taxane in either an adjuvant or metastatic setting. Other drugs used to treat anthracycline- and taxane-refractory metastatic breast cancer include capecitabine (Xeloda), gemcitabine (Gemzar, and others) and vinorelbine (Navelbine, and others).

Bevacizumab (Avastin - Genentech) is a recombinant humanized monoclonal antibody that binds to vascular endothelial growth factor and prevents it from binding to receptors on endothelial cells, inhibiting formation of new blood vessels. Previously approved by the FDA for use in combination regimens for first-line treatment of metastatic colon cancer and metastatic non-small cell lung cancer, and used off-label for treatment of agerelated macular degeneration, it has now also been approved by the FDA for use in combination with paclitaxel (Taxol, and others) for first-line treatment of HER2-negative metastatic breast cancer.

Ixabepilone (ix ab ep' i lone; Ixempra - Bristol-Myers Squibb), a semisynthetic epothilone analog, has been approved by the FDA for treatment of advanced breast cancer. It is indicated for use in combination with capecitabine (Xeloda - Roche) for treatment of locally advanced or metastatic breast cancer after failure of an anthracycline such as doxorubicin (Adriamycin) and a taxane such as paclitaxel (Taxol, and others). It is also approved as monotherapy for treatment of metastatic or locally advanced breast cancer after an anthracycline, a taxane and capecitabine have failed.

Lapatinib (Tykerb - GlaxoSmithKline), an oral inhibitor of both HER-2 and epidermal growth factor receptor type 1 (EGFR-1 or ErbB-1), has been approved by the FDA for use in combination with capecitabine (Xeloda) to treat advanced or metastatic breast cancer that overexpresses HER-2 in patients who have received prior therapy that included an anthracycline, a taxane and trastuzumab (Herceptin), an intravenous monoclonal antibody that also inhibits HER-2.

A variety of cancer chemotherapy drugs are used, mostly in combination, for treatment of locally advanced and metastatic esophageal, gastric and colorectal cancers. The mechanism of action, indications and adverse effects of some of these drugs are discussed in thei article.

In addition to surgery and radiation therapy, a variety of drugs are used both singly and in combination to treat breast cancer. This article summarizes the principles of adjuvant therapy and treatment for metastatic disease. A summary of individual drugs and their adverse effects begins on page 3.

The tables in this article list drugs used for treatment of cancer in the USA and Canada and their major adverse effects. The choice of drugs in Table I is based on the opinions of Medical Letter consultants. Some drugs are listed for indications for which they have not been approved by the US Food and Drug Administration. In some cases, such as elderly patients or those with many co-morbid illnesses, the regimen of choice might not be suitable. For many of the cancers listed, surgery and/or radiation therapy may be the treatment of choice or may also be part of the management. Anticancer drugs and their adverse effects are listed in Table II on page 46. A partial list of brand names appears on page 52.

The tables in this article list drugs used for treatment of cancer in the USA and Canada. The choices of drugs in Table 1 is based on the opinions of Medical Letter consultants. Some drugs are listed for indications for which they have not been approved by the US Food and Drug Administration. For many of the cancers listed, surgery and/or radiation therapy are also part of the management of the disease.

Trastuzumab (Herceptin - Genentech), a recombinant 'humanized' monoclonal antibody (rhuMAb) that binds to a protein encoded by the oncogene HER2, and capecitabine (ka pe site' a been; Xeloda - Roche), an oral pro-drug for 5-fluorouracil, have been approved by the FDA for treatment of metastatic breast cancer.