David L. Morse

United States Food and Drug Administration Drug Approval Summary: Gefitinib (ZD1839; Iressa) Tablets

On May 5, 2003, gefitinib (Iressa; ZD1839) 250-mg tablets (AstraZeneca Inc.) received accelerated approval by the United States Food and Drug Administration as monotherapy for patients with locally advanced or metastatic non-small cell lung cancer after failure of both platinum-based and docetaxel chemotherapies. Information provided in this summary includes chemistry manufacturing and controls, clinical pharmacology, and clinical trial efficacy and safety results. Gefitinib is an anilinoquinazoline compound with the chemical name 4-quinazolinamine,N-(3-chloro-4-flurophenyl)-7-methoxy-6-[3-(4-morpholinyl)propoxy]. It has the molecular formula C22H24ClFN4O3. Gefitinib is often referred to as a “specific” or “selective” inhibitor of epidermal growth factor receptor. Studies demonstrate, however, that gefitinib inhibits the activity of other intracellular transmembrane tyrosine-specific protein kinases at concentrations similar to those at which it inhibits the epidermal growth factor signal. Maximum plasma concentrations resulting from clinically relevant doses are 0.5–1 μm or more, well within the IC50 values of several tyrosine kinases. No clinical studies have been performed that demonstrate a correlation between epidermal growth factor receptor expression and response to gefitinib. Gefitinib is 60% available after oral administration and is widely distributed throughout the body. Gefitinib is extensively metabolized in the liver by cytochrome P450 3A4 enzyme. Over a 10-day period, approximately 86% of an orally administered radioactive dose is recovered in the feces, with <4% of the dose in the urine. After daily oral administration, steady-state plasma levels are reached in 10 days and are 2-fold higher than those achieved after single doses. Gefitinib effectiveness was demonstrated in a randomized, double-blind, Phase II, multicenter trial comparing two oral doses of gefitinib (250 versus 500 mg/day). A total of 216 patients were enrolled. The 142 patients who were refractory to or intolerant of a platinum and docetaxel comprised the evaluable population for the efficacy analysis. A partial tumor response occurred in 14% (9 of 66) of patients receiving 250 mg/day gefitinib and in 8% (6 of 76) of patients receiving 500 mg/day gefitinib. The overall objective response rate (RR) for both doses combined was 10.6% (15 of 142 patients; 95% confidence interval, 6.0–16.8%). Responses were more frequent in females and in nonsmokers. The median duration of response was 7.0 months (range, 4.6–18.6+ months). Other submitted data included the results of two large trials conducted in chemotherapy-naive, stage III and IV non-small cell lung cancer patients. Patients were randomized to receive gefitinib (250 or 500 mg daily) or placebo, in combination with either gemcitabine plus cisplatin (n = 1093) or carboplatin plus paclitaxel (n = 1037). Results from this study showed no benefit (RR, time to progression, or survival) from adding gefitinib to chemotherapy. Consequently, gefinitib is only recommended for use as monotherapy. Common adverse events associated with gefitinib treatment included diarrhea, rash, acne, dry skin, nausea, and vomiting. Interstitial lung disease has been observed in patients receiving gefitinib. Worldwide, the incidence of interstitial lung disease was about 1% (2% in the Japanese post-marketing experience and about 0.3% in a United States expanded access program). Approximately one-third of the cases have been fatal. Gefitinib was approved under accelerated approval regulations on the basis of a surrogate end point, RR. No controlled gefitinib trials, to date, demonstrate a clinical benefit, such as improvement in disease-related symptoms or increased survival. Accelerated approval regulations require the sponsor to conduct additional studies to verify that gefitinib therapy produces such benefit.

Bicarbonate Increases Tumor pH and Inhibits Spontaneous Metastases

The external pH of solid tumors is acidic as a consequence of increased metabolism of glucose and poor perfusion. Acid pH has been shown to stimulate tumor cell invasion and metastasis in vitro and in cells before tail vein injection in vivo. The present study investigates whether inhibition of this tumor acidity will reduce the incidence of in vivo metastases. Here, we show that oral NaHCO(3) selectively increased the pH of tumors and reduced the formation of spontaneous metastases in mouse models of metastatic breast cancer. This treatment regimen was shown to significantly increase the extracellular pH, but not the intracellular pH, of tumors by (31)P magnetic resonance spectroscopy and the export of acid from growing tumors by fluorescence microscopy of tumors grown in window chambers. NaHCO(3) therapy also reduced the rate of lymph node involvement, yet did not affect the levels of circulating tumor cells, suggesting that reduced organ metastases were not due to increased intravasation. In contrast, NaHCO(3) therapy significantly reduced the formation of hepatic metastases following intrasplenic injection, suggesting that it did inhibit extravasation and colonization. In tail vein injections of alternative cancer models, bicarbonate had mixed results, inhibiting the formation of metastases from PC3M prostate cancer cells, but not those of B16 melanoma. Although the mechanism of this therapy is not known with certainty, low pH was shown to increase the release of active cathepsin B, an important matrix remodeling protease.

Sorafenib for the Treatment of Advanced Renal Cell Carcinoma

Purpose: This report describes the U.S. Food and Drug Administration (FDA) review and approval of sorafenib (Nexavar, BAY43-9006), a new small-molecule, oral, multi-kinase inhibitor for the treatment of patients with advanced renal cell carcinoma (RCC). Experimental Design: After meeting with sponsors during development studies of sorafenib, the FDA reviewed the phase 3 protocol under the Special Protocol Assessment mechanism. Following new drug application submission, FDA independently analyzed the results of two studies in advanced RCC: a large, randomized, double-blinded, phase 3 international trial of single-agent sorafenib and a supportive phase 2 study. Results: In the phase 3 trial, 902 patients with advanced progressive RCC after one prior systemic therapy were randomized to 400 mg sorafenib twice daily plus best supportive care or to a matching placebo plus best supportive care. Primary study end points included overall survival and progression-free survival (PFS). A PFS analysis, pre-specified and conducted after a total of 342 events, showed statistically significant superiority for the sorafenib group (median = 167 days) compared with that for the controls (median = 84 days, log-rank P < 0.000001); the sorafenib/placebo hazard ratio was 0.44 (95% confidence interval, 0.35-0.55). Results were similar regardless of patient risk score, performance status, age, or prior therapy. The (partial) response rate to sorafenib was 2.1%. Overall survival results are preliminary. The principal toxicities in the sorafenib patients included reversible skin rashes in 40% and hand-foot skin reaction in 30%; diarrhea was reported in 43%, treatment-emergent hypertension was reported in 17%, and sensory neuropathic changes were reported in 13%. Grade 4 adverse events were uncommon. Grade 3 adverse events were hand-foot skin reaction (6%), fatigue (5%), and hypertension (3%). Laboratory findings included asymptomatic hypophosphatemia in 45% of sorafenib patients versus 11% in the placebo arm and elevation of serum lipase in 41% of sorafenib patients versus 30% in the placebo arm. Grade 4 pancreatitis was reported in two sorafenib patients, although both patients subsequently resumed sorafenib, with one at full dose. Conclusions: Sorafenib received FDA regular approval on December 20, 2005 for the treatment of advanced RCC based on the persuasive magnitude of improvement in PFS with acceptable safety. The recommended dose is 400 mg (two 200-mg tablets) twice daily taken either 1 h before or 2 h after meals. Adverse events were accommodated by temporary dose interruptions or reductions.

Sprycel for Chronic Myeloid Leukemia and Philadelphia Chromosome–Positive Acute Lymphoblastic Leukemia Resistant to or Intolerant of Imatinib Mesylate

Purpose: On June 28, 2006, the U.S. Food and Drug Administration approved dasatinib (Sprycel; Bristol-Myers Squibb), a new small-molecule inhibitor of multiple tyrosine kinases, for the treatment of adults with chronic phase, accelerated phase, or myeloid or lymphoid blast phase chronic myeloid leukemia (CML) or Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ ALL) with resistance or intolerance to prior therapy including imatinib. This summary reviews the database supporting this approval. Experimental Design: Four single-arm multicenter studies supported the efficacy and safety of dasatinib. The primary efficacy end point in chronic phase CML was major cytogenetic response. The primary end point in accelerated phase, myeloid phase, and lymphoid blast phase CML, and Ph+ ALL was major hematologic response. Results: The four studies combined enrolled 445 patients. In patients with chronic phase CML, the major cytogenetic response rate was 45% with a complete cytogenetic response rate of 33%. Major hematologic response rates in patients with accelerated phase CML, myeloid CML, lymphoid blast CML, and Ph+ ALL were 59%, 32%, 31%, and 42%, respectively. Median response durations in chronic phase, accelerated phase, and myeloid phase CML had not been reached. The median durations of major hematologic response were 3.7 months in lymphoid blast CML and 4.8 months in Ph+ ALL. Common toxicities with dasatinib included myelosuppression, bleeding, and fluid retention. Conclusions: This report describes the Food and Drug Administration review supporting the approval of dasatinib for CML and Ph+ ALL based on the rates and durability of cytogenetic and hematologic responses.

Docetaxel induces cell death through mitotic catastrophe in human breast cancer cells.

Apoptosis has long been considered to be the prevailing mechanism of cell death in response to chemotherapy. Currently, a more heterogeneous model of tumor response to therapy is acknowledged wherein multiple modes of death combine to generate the overall tumor response. The resulting mechanisms of cell death are likely determined by the mechanism of action of the drug, the dosing regimen used, and the genetic background of the cells within the tumor. This study describes a nonapoptotic response to docetaxel therapy in human breast cancer cells of increasing cancer progression (MCF-10A, MCF-7, and MDA-mb-231). Docetaxel is a microtubule-stabilizing taxane that is being used in the clinic for the treatment of breast and prostate cancers and small cell carcinoma of the lung. The genetic backgrounds of these cells were characterized for the status of key pathways and gene products involved in drug response and cell death. Cellular responses to docetaxel were assessed by characterizing cell viability, cell cycle checkpoint arrest, and mechanisms of cell death. Mechanisms of cell death were determined by Annexin V binding and scoring of cytology-stained cells by morphology and transmission electron microscopy. The primary mechanism of death was determined to be mitotic catastrophe by scoring of micronucleated cells and cells undergoing aberrant mitosis. Other, nonapoptotic modes of death were also determined. No significant changes in levels of apoptosis were observed in response to docetaxel.

Thermostability of firefly luciferases affects efficiency of detection by in vivo bioluminescence.

Luciferase from the North American firefly (Photinis pyralis) is a useful reporter gene in vivo, allowing noninvasive imaging of tumor growth, metastasis, gene transfer, drug treatment, and gene expression. Luciferase is heat labile with an in vitro halflife of approximately 3 min at 37 degrees C. We have characterized wild type and six thermostabilized mutant luciferases. In vitro, mutants showed half-lives between 2- and 25-fold higher than wild type. Luciferase transfected mammalian cells were used to determine in vivo half-lives following cycloheximide inhibition of de novo protein synthesis. This showed increased in vivo thermostability in both wild-type and mutant luciferases. This may be due to a variety of factors, including chaperone activity, as steady-state luciferase levels were reduced by geldanamycin, an Hsp90 inhibitor. Mice inoculated with tumor cells stably transfected with mutant or wild-type luciferases were imaged. Increased light production and sensitivity were observed in the tumors bearing thermostable luciferase. Thermostable proteins increase imaging sensitivity. Presumably, as more active protein accumulates, detection is possible from a smaller number of mutant transfected cells compared to wild-type transfected cells.

Heterobivalent Ligands Crosslink Multiple Cell-Surface Receptors: The Human Melanocortin-4 and δ-Opioid Receptors†

Cell-surface receptor mediated signaling is mechanistically complex. Hetero- and homo-multimerization of receptors appears to occur naturally and is a significant regulatory component of signal transduction.[1] Additionally, exogenous entities, such as cells and viruses, can interact with multiple heterologous receptors and induce clustering.[2] Such multivalent interactions are characterized by enhanced affinities (avidities) relative to monovalent binding and enhanced specificities with heteromultivalent interactions. For example, polymers containing α-MSH (α-melanocyte stimulating hormone) ligands bind with higher affinity to melanoma cells compared to monovalent α-MSH ligands.[3–5] Recapitulation of these natural phenomena using synthetic multivalent agents has been proposed for many years.[3–9] Although homomultivalent agents are known, there is little precedent for synthetic heteromultivalent targeting of cell-surface receptors. Herein we detail the synthesis and bioevaluation of heterobivalent ligands (htBVLs) targeted to two heterologous cell-surface receptors.

Noninvasive Detection of Breast Cancer Lymph Node Metastasis Using Carbonic Anhydrases IX and XII Targeted Imaging Probes

Purpose: To develop targeted molecular imaging probes for the noninvasive detection of breast cancer lymph node metastasis. Experimental Design: Six cell surface or secreted markers were identified by expression profiling and from the literature as being highly expressed in breast cancer lymph node metastases. Two of these markers were cell surface carbonic anhydrase isozymes (CAIX and/or CAXII) and were validated for protein expression by immunohistochemistry of patient tissue samples on a breast cancer tissue microarray containing 47 normal breast tissue samples, 42 ductal carcinoma in situ, 43 invasive ductal carcinomas without metastasis, 46 invasive ductal carcinomas with metastasis, and 49 lymph node macrometastases of breast carcinoma. Targeted probes were developed by conjugation of CAIX- and CAXII-specific monoclonal antibodies to a near-infrared fluorescent dye. Results: Together, these two markers were expressed in 100% of the lymph node metastases surveyed. Selectivity of the imaging probes were confirmed by intravenous injection into nude mice-bearing mammary fat pad tumors of marker-expressing cells and nonexpressing cells or by preinjection of unlabeled antibody. Imaging of lymph node metastases showed that peritumorally injected probes detected nodes harboring metastatic tumor cells. As few as 1,000 cells were detected, as determined by implanting, under ultrasound guidance, a range in number of CAIX- and CAXII-expressing cells into the axillary lymph nodes. Conclusion: These imaging probes have potential for noninvasive staging of breast cancer in the clinic and elimination of unneeded surgery, which is costly and associated with morbidities. Clin Cancer Res; 18(1); 207–19. ©2011 AACR.

Imaging the extracellular pH of tumors by MRI after injection of a single cocktail of T 1 and T 2 contrast agents

The extracellular pH (pHe) of solid tumors is acidic, and there is evidence that an acidic pHe is related to invasiveness. Herein, we describe an MRI single‐infusion method to measure pHe in gliomas using a cocktail of contrast agents (CAs). The cocktail contained gadolinium–1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraaminophosphonate (GdDOTA‐4AmP) and dysprosium–1,4,7,10‐tetraazacyclododecane‐N,N′,N′′,N′′′‐tetrakis(methylenephosphonic acid) (DyDOTP), whose effects on relaxation are sensitive and insensitive to pH, respectively. The Gd‐CA dominated the spin–lattice relaxivity ΔR1, whereas the Dy‐CA dominated the spin–spin relaxivity ΔR2*. The ΔR2* effects were used to determine the pixel‐wise concentration of [Dy] which, in turn, was used to calculate a value for [Gd] concentration. This value was used to convert ΔR1 values to the molar relaxivity Δr1 and, hence, pHe maps. The development of the method involved in vivo calibration and measurements in a rat brain glioma model. The calibration phase consisted of determining a quantitative relationship between ΔR1 and ΔR2* induced by the two pH‐independent CAs, gadolinium–diethylenetriaminepentaacetic acid (GdDTPA) and DyDOTP, using echo planar spectroscopic imaging (EPSI) and T1‐weighted images. The intensities and linewidths of the water peaks in EPSI images were affected by CA and were used to follow the pharmacokinetics. These data showed a linear relationship between inner‐ and outer‐sphere relaxation rate constants that were used for CA concentration determination. Nonlinearity in the slope of the relationship was observed and ascribed to variations in vascular permeability. In the pHe measurement phase, GdDOTA‐4AmP was infused instead of GdDTPA, and relaxivities were obtained through the combination of interleaved T1‐weighted images (R1) and EPSI for ΔR2*. The resulting r1 values yielded pHe maps with high spatial resolution. Copyright

Approval Summary: Nelarabine for the Treatment of T-Cell Lymphoblastic Leukemia/Lymphoma

Purpose: To describe the clinical studies, chemistry manufacturing and controls, and clinical pharmacology and toxicology that led to Food and Drug Administration approval of nelarabine (Arranon) for the treatment of T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma. Experimental Design: Two phase 2 trials, one conducted in pediatric patients and the other in adult patients, were reviewed. The i.v. dose and schedule of nelarabine in the pediatric and adult studies was 650 mg/m2/d daily for 5 days and 1,500 mg/m2 on days 1, 3, and 5, respectively. Treatments were repeated every 21 days. Study end points were the rates of complete response (CR) and CR with incomplete hematologic or bone marrow recovery (CR*). Results: The pediatric efficacy population consisted of 39 patients who had relapsed or had been refractory to two or more induction regimens. CR to nelarabine treatment was observed in 5 (13%) patients and CR+CR* was observed in 9 (23%) patients. The adult efficacy population consisted of 28 patients. CR to nelarabine treatment was observed in 5 (18%) patients and CR+CR* was observed in 6 (21%) patients. Neurologic toxicity was dose limiting for both pediatric and adult patients. Other severe toxicities included laboratory abnormalities in pediatric patients and gastrointestinal and pulmonary toxicities in adults. Conclusions: On October 28, 2005, the Food and Drug Administration granted accelerated approval for nelarabine for treatment of patients with relapsed or refractory T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma after at least two prior regimens. This use is based on the induction of CRs. The applicant will conduct postmarketing clinical trials to show clinical benefit (e.g., survival prolongation).