拉帕替尼:作用于表皮生长因子受体的靶向抗肿瘤新药

人表皮生长因子受体1和2(EGFR和HER2)与多种恶性肿瘤的发生和发展密切相关,成为抗肿瘤药物作用的靶点,针对这两个靶点的药物开发已成为抗肿瘤药物的研究热点之一,已有一系列相关药物应用于临床治疗。拉帕替尼是近年开发的针对EGFR和HER的双靶点抗肿瘤新药物,已在部分国家或地区上市,目前主要联合卡培他滨用于先期接受过蒽酮类抗生素、紫杉醇和曲妥珠单抗的HER2阳性乳腺癌的治疗,对于晚期或转移性乳腺癌疗效显著。本文主要综述了拉帕替尼的抗癌机制、临床研究进展和应用前景。     

靶向HER2药物治疗胃癌的研究概况

进展期胃癌的预后仍然较差。目前资料明确提示,如果没有对疾病生物学特征的深刻理解,新发展的药物几乎不可能成功。随着对肿瘤相关分子信号通路的深入研究,以关键分子通路中的某些关键分子为靶点的生物制剂得到开发与应用。抗人类表皮生长因子(HER)2药物曲妥珠单抗在进展期胃癌患者中应用的Ⅲ期临床试验中取得了阳性结果,证实了这种方法的有效性。目前有不少靶向HER2药物治疗胃癌的临床试验已经结束或正在进行。     

An Open‐Label Safety Study of Lapatinib Plus Trastuzumab Plus Paclitaxel in First‐Line HER2‐Positive Metastatic Breast Cancer

Background.

Recent data support the hypothesis that combining lapatinib and trastuzumab with taxane chemotherapy may offer added clinical benefit to patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). This study examined the safety of the triplet combination in first-line HER2-positive MBC.

Patients and Methods.

Patients were enrolled into three sequential cohorts; the last two cohorts were added by protocol amendment following review of safety data from cohort 1. Patients in cohort 1 received lapatinib (1000 mg/day) plus paclitaxel (80 mg/m² per week, 3 of every 4 weeks); cohort 2 received lapatinib (1000 mg/day) plus paclitaxel (70 mg/m² per week, 3 of every 4 weeks); and cohort 3 received lapatinib (750 mg/day) plus paclitaxel (80 mg/m² per week, 3 of every 4 weeks). All received standard trastuzumab dosing. The primary objective was assessment of dose-limiting toxicities, safety, and tolerability of this combination.

Results.

The most frequent adverse events (AEs) for all cohorts were diarrhea (89%), rash (79%), fatigue (73%), alopecia (63%), nausea (63%), and vomiting (40%). In cohorts 1 and 2, the incidence of grade 3 diarrhea was 62% and 50%, respectively; in cohort 3, the incidence was 25% (with prophylactic loperamide). Dehydration was the most frequent serious AE (10%). Across cohorts, overall response rate was 75%.

Conclusions.

The dose-limiting toxicity of paclitaxel, trastuzumab, and lapatinib in first-line HER2-positive MBC was diarrhea. Of the triplet combinations tested, the cohort receiving 750 mg/day dose of lapatinib had the lowest incidence of diarrhea; therefore, this dose should be used in further studies on the treatment of MBC.     

The HER2 amplicon includes several genes required for the growth and survival of HER2 positive breast cancer cells

About 20% of breast cancers are characterized by amplification and overexpression of the HER2 oncogene. Although significant progress has been achieved for treating such patients with HER2 inhibitor trastuzumab, more than half of the patients respond poorly or become resistant to the treatment. Since the HER2 amplicon at 17q12 contains multiple genes, we have systematically explored the role of the HER2 co-amplified genes in breast cancer cell growth and their relation to trastuzumab resistance. We integrated aCGH data of the HER2 amplicon from 71 HER2 positive breast tumors and 10 cell lines with systematic functional RNA interference analysis of 23 core amplicon genes with several phenotypic endpoints in a panel of trastuzumab responding and non-responding HER2 positive breast cancer cells. Silencing of HER2 caused a greater growth arrest and apoptosis in the responding compared to the non-responding cell lines, indicating that the resistant cells are inherently less dependent on the HER2 pathway. Several other genes in the amplicon also showed a more pronounced effect when silenced; indicating that expression of HER2 co-amplified genes may be needed to sustain the growth of breast cancer cells. Importantly, co-silencing of STARD3, GRB7, PSMD3 and PERLD1 together with HER2 led to an additive inhibition of cell viability as well as induced apoptosis. These studies indicate that breast cancer cells may become addicted to the amplification of several genes that reside in the HER2 amplicon. The simultaneous targeting of these genes may increase the efficacy of the anti-HER2 therapies and possibly also counteract trastuzumab resistance. The observed additive effects seem to culminate to both apoptosis and cell proliferation pathways indicating that these pathways may be interesting targets for combinatorial treatment of HER2+ breast cancers.     

Phase II trial of lapatinib and topotecan (LapTop) in patients with platinum-refractory/resistant ovarian and primary peritoneal carcinoma

Objective

Resistance to chemotherapy is a major challenge in the treatment of ovarian/peritoneal cancer. One purported mechanism of topotecan resistance is the breast cancer resistance protein (BCRP) and P-glycoprotein (Pgp). We designed a phase II clinical trial evaluating the efficacy and adverse event profile of concomitant topotecan and lapatinib, a small molecule pan-erbB inhibitor that can block BCRP/Pgp efflux of topotecan.

Methods

Patients with platinum-refractory or resistant epithelial ovarian/peritoneal cancer were treated with topotecan 3.2 mg/m2 IV on Day 1, 8 and 15 and lapatinib 1250 mg PO daily, continuously in 28 day cycles. The primary endpoint was response rate. For correlative studies, archived tissue was assessed for expression of EGFR, HER2, HIF-1α, CD31, and BCRP.

Results

Eighteen patients were enrolled and treated. Four experienced evidence of clinical benefit: one partial response and three with stable disease. Using a two-stage Simon design, the trial was stopped after the first stage due to insufficient activity. Grades 3+ and 4+ adverse events (AE) were experienced in 14 and 4 patients, respectively. The most common grade 3/4 AE were neutropenia (56%), thrombocytopenia (28%), and diarrhea (22%).

Conclusions

The combination of lapatinib plus topotecan for the treatment of platinum refractory/resistant epithelial ovarian cancer lacks sufficient activity to warrant further investigation. In particular, hematologic adverse events were substantial. Expression of correlative study markers did not reveal patterns of predicted benefit or toxicity. Disruption of erbB signaling and BCRP/Pgp efflux with lapatinib was insufficient for overcoming topotecan resistance, suggesting alternative mechanisms of resistance are involved.     

Treatment of HER2-positive breast cancer

The human epidermal growth factor receptor 2 gene (HER2) is overexpressed and/or amplified in ∼15% of breast cancer patients and was identified a quarter century ago as a marker of poor prognosis. By 1998, antibody therapy targeting the HER2 pathway was shown to demonstrably improve progression-free and overall survival in metastatic disease, and in 2005 evidence of improvement in disease-free and overall survival from the first generation of trastuzumab adjuvant trials became available. However, not all patients with HER2 overexpression benefit from trastuzumab. Second-generation studies in metastatic disease led to the approval of several new HER2-targeted therapies using small molecule tyrosine kinase inhibitors such as lapatinib, new HER2/HER3 antibodies such as pertuzumab, and the new antibody chemotherapy conjugate ado-trastuzumab emtansine. These successes supported the launch of second-generation adjuvant trials testing single and dual HER2-targeted agents, administered concomitantly or sequentially with chemotherapy that will soon complete accrual. HER2-positive breast cancer in the setting of HER2-targeted therapy is no longer associated with poor prognosis, and recent guidance by the US Food and Drug Administration suggests that pathologic response to HER2-targeted therapy given preoperatively may allow an earlier assessment of their clinical benefit in the adjuvant setting. An adjuvant trial of trastuzumab in patient whose tumors express normal levels of HER2 and trials of single/dual HER2-targeting without chemotherapy are also ongoing. In this article, we review the current data on the therapeutic management of HER2-positive breast cancer.     

The combination of an mTORc1/TORc2 inhibitor with lapatinib is synergistic in bladder cancer in vitro

ObjectiveTo examine the ability of dual mTORc1/c2 inhibitors in conjunction with lapatinib to function in a synergistic manner to inhibit cell proliferation and anchorage-independent growth in bladder cancer cell lines.Materials and methodsWe examined patient tumor samples for overexpression of pS6, p4EBP1, pAkt, and phosphorylated epidermal growth factor receptor (pEGFR) using a tissue microarray containing 84 cases. Three bladder cancer cell lines, T24, HT1376, and UM-UC-3, were analyzed for cell proliferation after treatment with mTORc1/c2 inhibitors OSI-027 or PP242. Western blots were used to verify that the drugs were inhibiting phosphorylation of target proteins within the mTOR pathway, and they were compared with rapamycin inhibition. We also analyzed cell proliferation and anchorage-independent growth after treatment with OSI-027 and lapatinib in combination. PARP cleavage and autophagic flux were measured by examining levels of LC3B and p62 by western blotting.ResultsTumor samples show increased expression of pEGFR (38% vs. 8%) and HER2 (38% vs. 4%) and decreased expression of pAkt S473 (7.5% vs. 29%) and pAkt T308 (50% vs. 84%) relative to normal tissue. Significant differences between normal and tumor samples for staining with pEGFR (P = 0.0188), HER 2 (P = 0.0017), pATK S473 (P = 0.0128), and pAkt T308 (P = 0.0015) is observed. Expression of proteins within the EGFR/HER2 pathway or within the mTOR pathway is correlated. No correlation was found between staining and tumor stage. OSI-027 and PP242 diminish cell proliferation in all 3 cell lines with IC₅₀ values ranging from 0.63 to 17.95 µM. Both drugs inhibit phosphorylation of both mTORc1 and mTORc2 pathway components. OSI-027 and lapatinib inhibit cell proliferation and anchorage-independent growth in a synergistic manner. One cell line exhibited apoptosis in response to combination drug treatment, whereas the other 2 cell lines have increased levels of autophagy indicative of resistance to apoptosis.ConclusionsThe combination of OSI-027 and lapatinib results in antitumor synergy and further exploration of this combination should be undertaken.     

Next generation molecular targeted agents for breast cancer: focus on EGFR and VEGFR pathways

Here we reviewed the recent progress of molecular targeting drugs, including trastuzumab, lapatinib, erlotinib and bevacituzumab. Fortunately, Her-2 positive cases of metastatic or relapsed cases, those with the worse prognosis, are responsive to trastuzumab-based chemotherapy. Lapatinib will likely be effective against trastuzumab-resistant cases and brain metastases. Furthermore, the introduction of bevacituzumab will improve VEGF-VEGFR- associated tumor growth.