Patrick J. Medina

Lapatinib : A Dual Inhibitor of Human Epidermal Growth Factor Receptor Tyrosine Kinases

BACKGROUND Lapatinib, the first dual inhibitor of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) tyrosine kinases, was approved by the US Food and Drug Administration (FDA) in 2007. It is indicated for use in combination with capecitabine for the treatment of patients with advanced breast cancer or metastatic breast cancer (MBC) whose tumors overexpress HER2 (ErbB2) and who have received previous treatment that included an anthracycline, a taxane, and trastuzumab. OBJECTIVE This review summarizes the pharmacology, pharmacokinetics, clinical efficacy, and safety profile of lapatinib, and its current and potential role in the treatment of breast cancer and other malignancies. METHODS Relevant English-language publications were identified through searches of MEDLINE (1966-May 2008),the American Society of Clinical Oncology abstracts database (2000-2007), abstracts from the San Antonio Breast Cancer Symposium (2005-2007), and the FDA Web site (January 2008). Search terms included lapatinib, GW572016, HER2, EGFR, receptor tyrosine kinase, dual-receptor blockade, adverse events, and clinical trials. RESULTS The T(max) of lapatinib after oral administration is 3 to 4 hours. Dividing the dose or administering it with food, particularly a high-fat meal, increases the AUC >2-fold. Lapatinib is metabolized primarily by the cytochrome P450 3A4 isozyme, with 1 metabolite remaining active against EGFR but not HER2. Due to drug accumulation, the t(1/2) of lapatinib is 24 hours with continuous dosing. In a Phase III trial comparing lapatinib and capecitabine with capecitabine alone in women with HER2-positive, locally advanced breast cancer or MBC that had progressed after treatment with an anthracycline, a taxane, and trastuzumab, the combination of lapatinib and capecitabine was associated with a numeric improvement in response rate compared with capecitabine alone (22% vs 14%, respectively; P = NS) and a significant increase in time to progression (6.2 vs 4.3 months; hazard ratio = 0.57; 95% CI, 0.43-0.77; P < 0.001). Lapatinib has been reported to have antitumor activity in Phase II trials when used as first-line therapy for MBC, in patients with inflammatory breast cancer, and in patients with central nervous system metastases. Phase II trials in other solid tumor types found modest activity. The approved dosing of lapatinib is 1,250 mg PO QD given continuously in combination with capecitabine 2,000 mg/m(2) daily administered in 2 divided doses on days 1 to 14 of a 21-day cycle. The most common clinical toxicities of all grades associated with lapatinib used in combination with capecitabine in the pivotal clinical trial were diarrhea (65%), hand-foot syndrome (53%), nausea (44%), rash (29%), and fatigue (24%). Cardiac toxicity appears to be less frequent with lapatinib than with trastuzumab. CONCLUSIONS Lapatinib is a dual inhibitor of the EGFR and HER2 tyrosine kinases. It is approved by the FDA for use in combination with capecitabine for the treatment of HER2-positive MBC that has progressed with standard treatment. In clinical trials, this combination was associated with a significant improvement in the time to progression in patients with MBC. Lapatinibs efficacy in other malignancies that overexpress EGFR and/or HER2 is under evaluation.

Drug-associated thrombotic thrombocytopenic purpura-hemolytic uremic syndrome.

Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) is an inclusive term describing diverse syndromes of multiple etiologies with the common features of thrombocytopenia and microangiopathic hemolytic anemia. Other organ involvement, including renal failure, neurologic abnormalities, and gastrointestinal symptoms, is common. Adverse reactions to drugs increasingly are reported as a potential cause of TTP-HUS. More than 50 drugs and other substances have been associated with the development of TTP-HUS, but many case reports are difficult to interpret because there is uncertainty regarding the diagnosis of TTP-HUS and because there is uncertainty regarding the relation of drug exposure to the onset of TTP-HUS. A systematic analysis of reports of drug-associated TTP-HUS will be required to better understand the strength of clinical evidence linking drugs to the etiology of TTP-HUS. In this review, five drugs that have been the subject of the most and the most recent reports of drug-associated TTP-HUS are discussed: mitomycin C, cyclosporine, quinine, ticlopidine, and clopidogrel. The clinical features of TTP-HUS associated with these drugs are different, suggesting two principal mechanisms by which drugs may cause TTP-HUS: dose-related toxicity (mitomycin C, cyclosporine), and immune-mediated reaction (quinine, ticlopidine, clopidogrel). The role of plasma exchange is uncertain, but this treatment is appropriate because of the high mortality and morbidity of drug-associated TTP-HUS. Recognition of a drug-associated etiology in a patient with TTP-HUS is critical to avoid re-exposure and recurrent illness.

Bevacizumab: An Angiogenesis Inhibitor with Efficacy in Colorectal and Other Malignancies

OBJECTIVE: To review the pharmacology, pharmacokinetics, and pivotal clinical trials for bevacizumab, emphasizing its use in colorectal cancer. DATA SOURCES: A PubMed/MEDLINE search was conducted (1966—April 2004) using the following terms: bevacizumab, Avastin, anti-VEGF, anti-angiogenesis, and colorectal cancer. Additional data sources included meeting abstracts, bibliographies from identified articles, and information from the manufacturer. STUDY SELECTION AND DATA EXTRACTION: Preclinical and clinical trials that used bevacizumab for the treatment of colorectal cancer and other malignancies were selected from the data sources. All published, randomized clinical trials evaluating bevacizumab in colorectal cancer were included in this review. DATA SYNTHESIS: Despite advances in chemotherapy, current therapeutic options for metastatic disease provide only temporary benefit for most patients. Bevacizumab is the first anti-cancer agent shown to provide benefit for patients with cancer by inhibiting angiogenesis. Bevacizumab has shown significant activity in the treatment of many cancers, including metastatic colorectal cancer. When used in combination with fluorouracil-based chemotherapy, bevacizumab improves overall response rates, time to progression, and survival in patients with metastatic colorectal cancer. Common toxicities associated with bevacizumab include hypertension, bleeding episodes, and thrombotic events. CONCLUSIONS: Although clinical knowledge on the effectiveness of bevacizumab is limited, early data indicate that it is a promising agent, with a novel mechanism of action, for patients with metastatic cancer, including colorectal cancer.

Phase I Clinical and Pharmacologic Study of 13-cis-Retinoic Acid, Interferon Alfa, and Paclitaxel in Patients With Prostate Cancer and Other Advanced Malignancies

PURPOSE Recent studies demonstrate that retinoids decrease expression of the anti-apoptotic protein bcl-2, enhance the effect of chemotherapy, and act synergistically with interferon alfa (IFNalpha) to inhibit tumor cell growth in vitro. A phase I trial of 13-cis-retinoic acid (CRA), IFNalpha, and paclitaxel (TAX) was conducted to determine the toxicity and recommended phase II dose of this combination. Pharmacodynamic studies were performed to determine whether CRA and IFNalpha could modulate bcl-2 expression in vitro and in patients. PATIENTS AND METHODS Twenty-two patients with prostate cancer or other advanced malignancies were treated with CRA/IFNalpha and escalating doses of TAX. The effect of CRA/IFNalpha on TAX pharmacokinetics was analyzed in both patients and human liver microsomes. The effect of CRA/IFNalpha on bcl-2 expression was assessed in vitro and in peripheral-blood mononuclear cells (PBMCs) by immunoblotting. RESULTS CRA 1 mg/kg on days 1 to 4, IFNalpha 6 MU/m(2) subcutaneously on days 1 to 4, and TAX 175 mg/m(2) on day 3 was well tolerated. Pharmacokinetic studies demonstrated that CRA/IFNalpha caused a 33% decrease in TAX clearance and a 23% decrease in the area under the concentration-time curve values of the TAX metabolite 6-alfa-hydroxytaxol (6-HT). CRA alone reduced conversion of TAX to 6-HT by 41% in human liver microsomes. CRA/IFNalpha decreased bcl-2 expression in vitro and in PBMCs. CONCLUSION CRA/IFNalpha and TAX is a well-tolerated regimen. CRA/IFNalpha increases TAX area under the concentration-time curve through an inhibitory effect of CRA on the metabolism of TAX to 6-HT. CRA/IFNalpha can modulate bcl-2 expression in vitro and demonstrates similar biologic activity in patients. Further studies will determine the activity of CRA/IFNalpha/TAX and validate the assessment of bcl-2 in PBMCs as a marker of tumor response.

Mammalian target of rapamycin: Biological function and target for novel anticancer agents

PURPOSE The biological function of the mammalian target of rapamycin (mTOR) and mechanisms of action of mTOR inhibitors currently available for clinical use are described. SUMMARY mTOR is a target for anticancer agents due to its role in cancer development, progression, and resistance to other antineoplastic agents. Currently, two mTOR inhibitors, temsirolimus and everolimus, are approved for the treatment of patients with advanced renal cell carcinoma (RCC). Clinical trials comparing single-agent temsirolimus with interferon alfa-2a demonstrated an improvement in overall survival and progression-free survival (PFS) in patients with metastatic RCC. Clinical studies comparing everolimus with placebo indicated improved PFS in advanced RCC patients whose disease had progressed on or after vascular endothelial growth factor (VEGF) inhibitor therapy. Due to its role in the phosphatidylinositol 3-kinase (PI3K) signaling pathway, mTOR is a rational target for inhibition in combination with other agents, including traditional chemotherapy and agents that are affected by or target the PI3K pathway. Data from these studies review the use of mTOR inhibitors in non-Hodgkins lymphoma and endometrial, breast, and neuroendocrine tumors. Common toxicities of mTOR inhibitors include mucositis, stomatitis, rash, asthenia, fatigue, and myelosuppression. Additional toxicities requiring monitoring include hyperglycemia, hyperlipidemia, and pneumonitis. CONCLUSION The mTOR signaling pathway is upregulated in a variety of solid and hematologic tumors. Two inhibitors of this pathway, temsirolimus and everolimus, have been approved for use in metastatic RCC. Although relatively safe, these drugs are associated with some unique adverse effects, such as hyperlipidemia, hyperglycemia, and pneumonitis, that require monitoring and may require clinical intervention.

Effect of Docetaxel in Patients With Hormone-Dependent Prostate-Specific Antigen Progression After Local Therapy for Prostate Cancer

PURPOSE To evaluate docetaxel in the treatment of patients with early-stage prostate cancer with prostate-specific antigen (PSA) progression after local therapy without androgen ablation therapy. PATIENTS AND METHODS Twenty-five patients with adenocarcinoma of the prostate with PSA progression despite local therapy were treated with 70 mg/m2 docetaxel every 21 days. Treatment was planned for eight cycles. Patients were followed up for effects on PSA, testosterone, and toxicity. RESULTS Twenty-three of 25 patients completed at least one full cycle of therapy. Ten (43%) of 23 patients demonstrated a decrease in PSA by > or = 50% for at least 4 weeks. The nadir decrease in PSA occurred beyond 150 days of therapy in most patients. Therapy was well tolerated. Grade 4 neutropenia with fever occurred in only six cycles (4.5%). Two patients required 25% dose reductions, both occurring with cycle 6, secondary to increased transaminases in one patient, and grade 3 lacrimation in the other patient. Two patients were removed after the first cycle of therapy due to toxicity (deep venous thrombosis, chest palpitations). Mean testosterone levels were not reduced in 17 patients assessed before and during therapy (P = .12). CONCLUSION This study demonstrated the activity of docetaxel alone, without androgen ablation, in patients with PSA progression after completion of local therapy. Treatment with docetaxel in this population with early disease progression was well tolerated, biochemically active, and was not androgen ablative. Accrual to national phase III studies in early disease is now critical and should be strongly encouraged to determine the ability of early chemotherapy to improve survival.

PD-1 Pathway Inhibitors: Immuno-Oncology Agents for Restoring Antitumor Immune Responses.

Immune checkpoint inhibitors are designed to restore a patients own antitumor immune response that has been suppressed during tumor development. The first monoclonal antibodies against the immune checkpoint programmed death 1 (PD‐1) receptor, nivolumab and pembrolizumab, are now approved for clinical use. Both agents are indicated for the treatment of advanced melanoma, as well as for the treatment of metastatic non–small cell lung cancer (NSCLC). Nivolumab is also approved for the treatment of advanced renal cell carcinoma. In patients with melanoma, these agents result in objective response rates of ~25–40%, with durable responses lasting more than 2 years in some cases. Results from phase III trials have shown improved survival with nivolumab versus standard‐of‐care chemotherapy in both patients with advanced melanoma and those with advanced NSCLC. In patients with advanced melanoma, both PD‐1 inhibitors (nivolumab and pembrolizumab) have shown improved survival versus ipilimumab. PD‐1 inhibitors are associated with adverse events that have immune etiologies, with grade greater than 3 adverse events typically reported in 16% or less of patients. However, most immune‐mediated adverse events (including grade 3–4 adverse events) can be managed by using published management algorithms without permanent discontinuation of the agent. As nivolumab and pembrolizumab enter the clinic, and with more PD‐1 pathway agents in development for a range of tumor types, this review aims to provide pharmacists with a basic understanding of the role of PD‐1 in modulating the immune system and their use in the cancer treatment. The most recent clinical efficacy and safety data are discussed, highlighting the response characteristics distinctive to immune checkpoint inhibitors, along with pharmacokinetic and pharmacodynamic data and cost considerations.

Use of prescription and nonprescription medications and supplements by cancer patients during chemotherapy: questionnaire validation

Background. Cancer patients take medications for coexisting disease and self-medicate with over-the-counter drugs (OTCs). A complete analysis of the use of prescription drugs, OTCs, and supplements during cancer treatment has never been done. Methods. The study developed and validated a self-administered questionnaire on the use of concomitant medications by patients undergoing treatment with chemotherapy. The questionnaire listed 510 prescription medications, OTCs, and supplements (including vitamins, minerals, and herbs). Fifty-two subjects completed the questionnaire while visiting the infusion clinic to receive chemotherapy. On a subsequent visit the subjects brought their medications to the clinic and a pharmacist reviewed their completed questionnaire. Results. Ninety-six percent of the subjects reported taking prescription medications within 3 days prior to chemotherapy, 71% reported taking OTCs and 69% reported use of supplements. The subjects took an average of 5.5 (range 0—13) prescription drugs, 2.2 (0—20) OTCs, and 1.9 (0—11) supplements. Twenty-one drugs were each taken by at least 10% of the subjects. Acetaminophen was taken by 59.6% of the subjects. One subject reported taking five acetaminophen-containing drugs. The questionnaires sensitivity was 92.0%, specificity 99.9%. Conclusion. Within 3 days prior to chemotherapy, subjects took an average of 9.6 concomitant medications, many of which alter drug metabolism and or disposition. In clinical trials, multivariate analysis of all concomitant medications could add to clinically relevant data to identify drug interactions that negate or potentiate the efficacy of cancer treatment regimens. In some instances, apparent resistance of tumors to chemotherapy may be the result of drug interactions. J Oncol Pharm Practice (2008) 14: 123—130.

Clinical and Biological Activity of Soy Protein Powder Supplementation in Healthy Male Volunteers

Purpose: To determine if a commonly used soy protein supplement exhibits biological activity in vivo and in vitro, we evaluated an over-the-counter soy protein powder supplement using blood from healthy male volunteers and in an estrogen receptor in vitro assay. Subjects and Methods: We recruited healthy male volunteers 18 years of age or older that were in good health. Treatment consisted of consuming two scoops (56 g) of pure soy protein powder (Puritans Pride, Oakdale, NY) daily for 28 days. Serum testosterone and luteinizing hormone (LH) levels were collected on days −7, 0, 14, and 28 of therapy, and day 42. A reporter estrogen receptor (ER) assay was used to determine the effect on ER-β and ER-α in vitro. Results: Twelve subjects were enrolled with a mean age of 32.25 years (range 25 to 47). Serum testosterone decreased 19%(±22%) during the 4-week use of soy protein powder (P = 0.021) and increased within 2 weeks after we discontinued soy protein powder. Serum LH concentrations decreased during the 4-week use of soy protein powder then increased within 2 weeks after we stopped the soy protein powder, but the changes did not reach statistical significance (P = 0.20). Soy protein powder was found to induce agonist activity to ER-β using a reporter estrogen receptor assay in yeast. Conclusion: Soy protein powder decreases serum testosterone levels in healthy men and acts as an ER-β agonist; the significance of this biological effect with respect to cancer prevention needs further study. (Cancer Epidemiol Biomarkers Prev 2007;16(4):829–33)

Cetuximab hypersensitivity infusion reactions: Incidence and risk factors*

Introduction: Cetuximab is a chimeric mouse-human (30:70) IgG1 monoclonal antibody that competitively inhibits the binding of epidermal growth factor. Cetuximab is generally well tolerated; however, hypersensitivity infusion reactions have been reported. The incidence at the University of Oklahoma was currently unknown, though anecdotally high. The purpose of this study was to determine the incidence of severe HIRs and secondarily to determine risk factors for cetuximab-induced hypersensitivity infusion reactions. Methods and results: A retrospective chart review was conducted and included all patients that received cetuximab from 2005 to 2010 at the outpatient clinics of the Oklahoma University Health Sciences Center. A total of 153 patients were included in the analysis. The overall incidence proportion of severe hypersensitivity infusion reactions was 12.4%. Male patients had an increased incidence of severe hypersensitivity infusion reactions compared to female patients (20.6% vs. 5%, p = 0.0036). Current smokers had an increased incidence of severe hypersensitivity infusion reactions of 23.6% when compared to never smokers or former smokers, p = 0.0012. Cervical cancer had a significantly decreased risk of severe hypersensitivity infusion reactions when compared to other tumor types (5.3% vs. 16.7%, p = 0.0387). Multivariate analysis identified risk factors associated with severe HIRs to be: male gender, RR = 3.9, p = 0.01 and current smokers, RR = 3.98, p = 0.0048. Conclusion: Patients at the University of Oklahoma had an increased incidence of severe hypersensitivity infusion reactions when compared to the national average. Male patients and current smokers were found to be at increased risk for severe hypersensitivity infusion reactions in our study. Further investigation is warranted.