Production and approval of trastuzumab (HerceptinÒ) for the treatment of metastatic breast cancer (MBC) was a millstone in antibody-based Targeted therapy in the cancer treatment. However, despite the early success in the clinical trials, trastuzumab failed to appreciate the initial attraction due to development of resistance to the drug. Majority of patients who benefit from the drug acquire resistance to it and experience tumor recurrence within 1 year. Several molecular and cellular mechanisms underlying the resistance to trastuzumab have been proposed. In this review, first, we provide a brief history leading to production of trastuzumab. Also we consider the cellular and molecular antitumor effects of trastuzumab and then, we discuss the mechanisms underlying trastuzumab resistance in four levels.

Cancer is one of the most dangerous health problems of today modern societieswhich has an increasing rate especially in developing countries. There are manydiverse ongoing treatment attempts trying to defeat cancer. Despite that, scientistshave been unable to find a permanent cure for this disease. In many cases althoughthere is a successful first response in patients, cancer cells are finally able towithstand therapeutic procedures and even use chemo-resistance to take advantageof treatments to facilitate tumor growth, resulting in cancer remission. Therefore, andmostly in recent two decades, scientists have been trying to choose their treatmentsjust as smart to be able to conquer cancer. One of the best methods of this smartdefense is to target weak points of neoplastic cells and use them for designing drugs. In this case it would be most probable for cancer cells not to have a chance to confrontand cause chemo-resistance. Total endeavors to fulfill this goal are named “ Targetedcancer therapy” . This therapeutic approach is mostly consisted of two differentprocedures: 1-designing and using specific drugs to target cancer cells’ mutatedgenes; which will be defined by checking the genetic background of tumor cells foreach specific cancer type. EGFR, RAS, VEGF and HIF-1α are among the pathwaysthat have already been used as targets. 2-The other procedure could be methods thatwould carry drugs directly to unhealthy cells to prevent further side effects for normalcells of patients. It would be possible by designing specific antibodies to targetantigens of neoplastic cells. Ribonucleic sequences (miRNAs and siRNAs) are alsovery promising as new drugs and nanoparticles have enabled us to increase drugconcentration in tumors. The ultimate goal of these new experiments is to suggestspecific drugs for each patient based on the nature of one's disease and geneticbackground, which will bring about "personalized medicine" era. Using valid newreferences, this review article first presents targets that are currently being used forthis Targeted therapy, their logic of choice and the drugs that have already beenproduced for clinical trials. Smart methods of drug delivery are also presented anddiscussed afterwards.

The spectrum of diseases caused by intracellular bacterial pathogens (IBPs) is broad, ranging from life-threatening conditions such as tuberculosis to other infectious-transmitted diseases. Conventional antibiotic treatment faces challenges due to antibiotic resistance, host cell toxicity, and limited drug penetration. Despite the excellent ability of these perilous pathogens to modulate host cell biology, localize in, and multiply through targeting the key virulence factors, cell brings about auspicious maneuvers to combat pathogenic diseases and alleviate their significant global burden. Modulation and identification of molecules, pathways, and responses are the initial steps of Targeted therapy, varying from disease to disease. This article explores the cutting-edge advancements in Targeted therapy approaches. Innovations such as nanoparticlebased drug delivery systems, phage therapy, immunomodulation, and gene editing, which hold a promising future for overcoming the limitations of traditional treatment, are also discussed. Efficient delivery systems, drug optimizations, and inch-perfect distribution and retention of therapeutic agents are some of the determining factors in the success of Targeted therapy for bacterial pathogens. The article also presents a novel application wherein filamentous phages are loaded as targets in nanocarriers for therapeutic purposes. The present challenges faced by the researchers, along with future directions for this field of medical science, are also outlined. Overall, the scope of this article involves the various strategies involved in Targeted therapy, drug modulations, and limitations faced in our current approaches.