{"id":421,"date":"2020-02-16T11:19:52","date_gmt":"2020-02-16T05:49:52","guid":{"rendered":"https:\/\/medicineplexus.com\/?p=421"},"modified":"2020-02-16T11:19:52","modified_gmt":"2020-02-16T05:49:52","slug":"evaluation-of-anti-cancer-drugs","status":"publish","type":"post","link":"https:\/\/medicineplexus.com\/evaluation-of-anti-cancer-drugs\/","title":{"rendered":"Evaluation of Anti-cancer Drugs"},"content":{"rendered":"\n<p><strong><em><u>Eval of anticancer:<\/u><\/em><\/strong><\/p>\n\n\n\n<p><strong>Need for new drugs<\/strong><\/p>\n\n\n\n<ul><li>Despite the major advances that have been made in the treatment of malignancy, many patients still die either from unresponsive tumors or recurrent disease<\/li><li>Need for anticancer drugs that would <strong>eradicate cancer cells without harming normal tissues<\/strong><\/li><li>Need for anticancer agents that would <strong>target resistant cancer cells<\/strong><\/li><\/ul>\n\n\n\n<ul><li><strong>Human tumor stem cell (HTSC) assay<\/strong>\/ <strong>Clonogenic Assay<\/strong><\/li><\/ul>\n\n\n\n<ul><li>Disease-orientated &#8211; model system incorporating multiple tumors cell of the same histotype<\/li><li><strong>Soft agar colony growth of freshly explanted human tissue is taken<\/strong><\/li><li><strong>Outcomes are based on growth inhibition<\/strong><\/li><li>Initial studies found that most drugs were active with the exception of drugs requiring systemic activation<\/li><li>HTSC assay &#8211; for evaluating efficacy of clinically active agents and individualizing cancer treatment<\/li><\/ul>\n\n\n\n<p><strong>Limitations<\/strong><\/p>\n\n\n\n<ul><li>Low plating efficiency of most solid tumors<\/li><li>There are no phase III clinical studies of individualized therapy demonstrating a significant increase in survival compared with empirically determined standard treatment<\/li><li>&nbsp;Therefore, the <strong>HTSC assay has not found a role in the individualization of patient therapy<\/strong><\/li><\/ul>\n\n\n\n<ul><li><strong>Human tumor cell line assay<\/strong><\/li><\/ul>\n\n\n\n<ul><li>The initial cell line panel incorporated a total of <strong>60 different human tumor cell lines<\/strong> of diverse histology<\/li><li>Different types of cancer <strong>including drug-resistant cell lines<\/strong> included<\/li><li>nonclonogenic protein stain <strong>sulfo-rhodamine B assay (38) is used to determine cell viability<\/strong><\/li><li>Each <strong>compound is tested over a 5-log concentration<\/strong> range against each of the 60 cell lines<\/li><li>These data generate characteristic profile or <strong>\u2018\u2018fingerprint\u2019\u2019 of cellular response, i.e.&nbsp; the \u2018\u2018mean graph\u2019\u2019<\/strong><\/li><li><strong>\u2018\u2018COMPARE\u2019\u2019<\/strong><strong> is a computerized, pattern recognition algorithm<\/strong> used in evaluating and exploiting the fingerprint data in order to determine the degree of similarity between mean graph profiles generated by similar or different compounds<\/li><\/ul>\n\n\n\n<p><strong>Implications<\/strong><\/p>\n\n\n\n<ul><li>The <strong>sensitivity of a cell line<\/strong>, along with knowledge of <strong>its molecular characteristics<\/strong> may indicate that a compound\u2019s action is mediated by its interaction with molecular target<\/li><li>Alternatively, <strong>differential expression<\/strong> in the form of a mean graph may indicate <strong>why particular cell lines may be resistant<\/strong><strong> to a test compound<\/strong><\/li><li>Endpoints \u2013<\/li><li>&nbsp;GI50 (concentration required to inhibit 50% of cells)<\/li><li>&nbsp;Total growth inhibition<\/li><li>&nbsp;LC50 (concentration&nbsp; required to kill 50% of cells)<\/li><\/ul>\n\n\n\n<p><strong>Limitations<\/strong><\/p>\n\n\n\n<ul><li>Factors other than the inherent chemo sensitivity of tumor cells significantly influence the outcome of chemotherapy in vivo (e.g., pharmacokinetics, tumor micro regions\/pH)<\/li><li><strong>Not&nbsp; sufficiently discriminatory<\/strong> to ensure that only a relatively small number of compounds would be selected for further evaluation in human tumor xenograft models<\/li><\/ul>\n\n\n\n<p><strong>Preclinical toxicity study<\/strong><\/p>\n\n\n\n<ul><li><strong>Aimed at predicting<\/strong><ul><li>Safe starting dose &amp; dosage regimen for human clinical trials(P1)<\/li><\/ul><ul><li>The toxicities of the compound, &amp;<\/li><\/ul><ul><li>The likely severity and reversibility of drug toxicities.<\/li><\/ul><\/li><li><strong>Regulatory requirement : <\/strong>Two acute preclinical toxicity studies<ul><li>Rodent (mice) &#8211; single- and multiple-dose lethality studies.<\/li><\/ul><ul><li>Non rodent (dogs) &#8211; single- and multiple-dose confirmatory toxicity.<\/li><\/ul><ul><li>Cytotoxic &amp; non cyotoxic drugs<\/li><\/ul><\/li><\/ul>\n\n\n\n<p><strong>Acute toxicity studies<\/strong><\/p>\n\n\n\n<ul><li>First mouse given a single injection (IP, IV, SC, IM or PO) of<strong> 400 mg\/kg <\/strong>(or lower if the compound is extremely potent)<\/li><li>Second mouse receives a dose of <strong>200 mg\/kg<\/strong> and a third mouse receives a single dose of <strong>100 mg\/kg<\/strong><\/li><li>The mice are observed for a period of <strong>2 weeks<\/strong><\/li><li>They are <strong>sacrificed if there are signs of significant toxicity<\/strong><\/li><li><strong>If all 3 mice must be sacrificed, the next 3 dose levels (50, 25 and 12.5 mg\/kg)<\/strong> are tested in a similar manner This process is repeated until a tolerated dose is found<\/li><li>This dose is then designated as <strong>MTD<\/strong><\/li><li>For the standard hollow fiber assay (HFA), the high and low dose levels are determined using the MTD the formula below<\/li><li><strong>High dose = [MTD x 1.5]\/4<\/strong><\/li><li><strong>Low dose = 0.67 x high dose<\/strong><\/li><\/ul>\n\n\n\n<p><strong>Hollow fiber assay<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"363\" height=\"237\" src=\"https:\/\/medicineplexus.com\/wp-content\/uploads\/2020\/02\/image-77.png?w=363\" alt=\"\" class=\"wp-image-422\" srcset=\"https:\/\/medicineplexus.com\/wp-content\/uploads\/2020\/02\/image-77.png 363w, https:\/\/medicineplexus.com\/wp-content\/uploads\/2020\/02\/image-77-300x196.png 300w\" sizes=\"(max-width: 363px) 100vw, 363px\" \/><\/figure>\n\n\n\n<ul><li><strong>Mice treated with experimental agents starting on day 4 following fiber implantation<\/strong> and continuing 4 days<\/li><li>Each agent&nbsp; administered by <strong>i.p injection at 2 dose levels<\/strong>. The doses are based on the maximum tolerated dose (MTD)<\/li><li>The fibers are collected from the mice and subjected to the MTT assay<\/li><li>The <strong>percent net growth in each treatment group is calculated<\/strong> and compared to the percent net growth in controls<\/li><li><strong>A 50% or greater reduction in percent net growth<\/strong> in the treated samples compared to the vehicle control samples is considered a <strong>positive result<\/strong><\/li><\/ul>\n\n\n\n<p><strong>Implications<\/strong><\/p>\n\n\n\n<ul><li>The HFA assesses the pharmacologic capacity of compounds to reach physiologic compartments and shows a <strong>practical means of quantifying viable tumor cell mass<\/strong><\/li><li>It is <strong>relatively rapid and cost-effective<\/strong> demonstration of in vivo activity<\/li><li>HFA as an in vivo prescreen is good predictor of in vivo xenograft activity which is the next step in preclinical screening<\/li><\/ul>\n\n\n\n<p><strong>Human tumor xenograft models<\/strong><\/p>\n\n\n\n<ul><li>Xenograft tumors are established by the <strong>s.c inoculation of tumor cells into nude mice<\/strong><\/li><li>Growth of solid tumors monitored using in situ caliper measurements<\/li><li>Activity is defined by<ul><li>Tumor growth delay<\/li><\/ul><ul><li>Net tumor cell kill T\/C ( T\/C &#8211; median treated tumor mass\/median control tumor mass)<\/li><\/ul><\/li><li>Drug-related deaths and body weight loss are used as parameters of toxicity<\/li><\/ul>\n\n\n\n<p><strong>Limitation<\/strong><\/p>\n\n\n\n<ul><li>Requirement for an immunocompromised host<\/li><li>Not all tumor systems can be studied by xenograft model<\/li><li>Inability of these models to fully resemble the complex relationship between the tumor and its microenvironment (e.g., angiogenesis)<\/li><li>Most importantly, the ability of xenografts to predict drug efficacy in human cancer patients has been disappointing<\/li><\/ul>\n\n\n\n<p><strong>Orthotopic and metastatic tumor models<\/strong><\/p>\n\n\n\n<ul><li><strong>Organ environment<\/strong> can influence the response of tumors to chemotherapy<\/li><li>As <strong>s.c. tumor models are not representative<\/strong> of the primary tumor site<\/li><li>&nbsp;In addition, <strong>clinically we treat well-established and advanced metastatic disease<\/strong><\/li><li>Thus, orthotopic tumor models seem to be <strong>more representative of a primary tumor with respect to tumor site and metastasis<\/strong><\/li><\/ul>\n\n\n\n<ul><li><strong>Advantage &#8211; <\/strong>orthotopic model is targeting processes involved in local invasion (eg, angiogenesis) &amp; is undertaken at a more clinically relevant site<\/li><li><strong>Disadvantage \u2013<\/strong><\/li><\/ul>\n\n\n\n<ol type=\"1\"><li>need for a high level of technical skill, time, and cost<\/li><li>Therapeutic efficacy more difficult to assess with orthotopic models in contrast to the relative ease of s.c. tumor&nbsp;<\/li><\/ol>\n\n\n\n<p><strong>Autochthonous models<\/strong><\/p>\n\n\n\n<ul><li>Autochthonous tumors include <strong>spontaneously occurring tumors and chemical, viral, or physical carcinogen-induced tumors<\/strong><\/li><li><strong>Advantages<\/strong> of autochthonous tumors include <strong>orthotopic growth, tumor histology devoid of transplantation introduced changes, and metastasis via lymphatic and vascular vessels<\/strong><\/li><li>Outcomes compared from autochthonous models and GEMs found that autochthonous models correlated best with clinical responses<\/li><\/ul>\n\n\n\n<p><strong>Limitations<\/strong><\/p>\n\n\n\n<ul><li>Autochthonous tumor models have an inherent variability in the time, frequency, number of tumor(s) induced and thus the number of animals required<\/li><li>Time required &#8211; several months to a year, as opposed to weeks with transplanted xenograft models<\/li><li>Thus, autochthonous tumor models are best reserved for confirmation<\/li><\/ul>\n\n\n\n<p><strong>Genetically engineered mouse models<\/strong><\/p>\n\n\n\n<ul><li>Genetically engineered mice are predisposed to cancer by introducing cellular\/viral oncogenes into the mouse germ line<\/li><li>Have highlighted the importance of specific oncogenes and tumor suppressor genes<\/li><li>GEM models resemble genetic\/molecular changes in human cancer &amp; are used to test novel anticancer therapeutics<\/li><li>Genes targeted to mouse embryonic stem cells, result in oncogene -bearing transgenic mice i.e., gene knockout mice<\/li><\/ul>\n\n\n\n<p><strong>Implications<\/strong><\/p>\n\n\n\n<ul><li>GEM models possess well validated drug targets and may potentially offer a more appropriate preclinical model<\/li><li>Additionally, GEM tumors develop autochthonously \/in situ and therefore may be more biologically representative of a particular tumor type in humans<\/li><\/ul>\n\n\n\n<p><strong>Limitations<\/strong><\/p>\n\n\n\n<ul><li>GEM models are expensive and time consuming<\/li><li>Their use is often restricted by intellectual property rights and patents<\/li><li>In addition to embryonic lethality, mice often do not develop the expected tumor type as they may die prematurely<\/li><li>The genetic background can affect transgene expression where outcome like rapidity of lesion ,type of lesion and tumor histiotype are affected by genetic background<\/li><\/ul>\n\n\n\n<ul><li>Clinical evaluation general points<\/li><li>Single arm studies<\/li><li>Non inferiority studies<\/li><li>Design for protectants<\/li><li>Endpoints<\/li><li><strong>DFS (Disease free survival):<\/strong> time from randomization to tumor recurrence or death d\/t any cause<ul><li>Used in the setting of-<\/li><\/ul><ul><li>After definitive t\/t<\/li><\/ul><ul><li>When a large percentage of patients achieve complete responses with chemotherapy<\/li><\/ul><ul><li>In situations where survival may be prolonged, making a survival endpoint impractical<\/li><\/ul><\/li><\/ul>\n\n\n\n<ul><li><strong>ORR (Objective response rate):<\/strong> proportion of patients with a tumor size reduction to a predefined amount<ul><li>ORR is a direct measure of drug antitumor activity, which can be evaluated in a single-arm study<\/li><\/ul><\/li><\/ul>\n\n\n\n<ul><li><strong>TTP (Time to progression):<\/strong> time from randomization until predefined tumor progression. Doesn\u2019t include death<\/li><\/ul>\n\n\n\n<ul><li><strong>PFS (Progression free survival):<\/strong> TTP and death<\/li><li>Whether an improvement in PFS represents a surrogate for clinical benefit depends on the magnitude of the effect &amp; risk-benefit compared to available therapies<\/li><li>Define tumor progression criteria in the protocol<\/li><li>Visits and radiological assessments should be symmetric between the two study arms to prevent systematic bias<\/li><li>Studies should be blinded<\/li><li><strong>TTF (Time to treatment failure):<\/strong> time from randomization to t\/t discontinuation d\/t any cause [disease progression, toxicity or death]. But it cannot be a regulatory endpoint since it doesn\u2019t distinguish efficacy from other parameters<\/li><\/ul>\n\n\n\n<ul><li><strong>Biomarkers<\/strong><\/li><li><strong>Generally,<\/strong> biomarkers assayed from blood or body fluids <strong>have not served as primary endpoints for cancer drug approval<\/strong><\/li><li><strong>Further research is needed to establish the validity of available biomarkers and determine whether improvements in biomarkers predict clinical benefit<\/strong><\/li><li>Biomarkers can be useful in identifying prognostic factors and stratification factors to be considered in study designs.<\/li><li>Phases<\/li><li>Phase 1:<\/li><li>Design: Conventional Fibonacci approach OR Statistically based dose escalation model.<\/li><li>Ethical issues.<\/li><li>Endpoints. Response rate, toxicity and clinically meaningful endpoints<\/li><li>Phase 2:<\/li><li>Randomized selection design<\/li><li>Design with reference standard t\/t control arm<\/li><li>Phase 2\/3 study design<\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Eval of anticancer: Need for new drugs Despite the major advances that have been made in the treatment of malignancy, many patients still die either from unresponsive tumors or recurrent disease Need for anticancer drugs that would eradicate cancer cells without harming normal tissues Need for anticancer agents that would target resistant cancer cells Human[&#8230;]\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","footnotes":""},"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts\/421"}],"collection":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/comments?post=421"}],"version-history":[{"count":0,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts\/421\/revisions"}],"wp:attachment":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/media?parent=421"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/categories?post=421"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/tags?post=421"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}