## 1 Introduction  
Cancer is one of the most serious global health problems, constituting the second major cause of death worldwide [1]. The development of new, safe, and effective agents for the management of cancer is still a challenge. Isatin (1\(H\)-indole-2,3-dione) is an endogenous compound in certain organisms and it was discovered in 1988 [2]. It received considerable attention in the medicinal arena because it is included in a number of bioactive heterocyclic compounds with diverse pharmacological profiles [3; 4; 5; 6; 7; 8]. A representative example of an already developed isatin-based anticancer drug isunitinib (I, Sutent(tm), Pfizer, Inc. New York, NY, USA, Figure 1), which was granted FDA approval in 2006 as an orally active multi-targeted tyrosine kinase inhibitor used for the management of imatinib-resistant gastrointestinal stromal tumors and metastatic renal-cell carcinoma [9; 10; 11]. Semaxanib (**II**) and orantinib (**III**) are other examples of isatin-based sunitinib analogs which were developed as new anticancer lead compounds via their multiple tyrosine kinase receptor inhibitory activity (Figure 1) [12].  
It has recently been reported that the symmetric bis-isatin derivative **IV** exhibited in vitro anti-proliferative activity toward the HepG2 cancer cell line with an IC\({}_{50}\) value of about 4.23 mM [13]. Accordingly, this represented a strong motif to synthesize the target compound **3** (Figure 2) being a non-symmetric bis-isatin derivative as a new anticancer candidate.  
Subsequently, and with the advancement of drug development in cancer management along with the synthesis of such potential anti-proliferative agents, numerous probable interactions should be considered. Concurrently, serum albumins, the multi-functional depots and transport carriers, are well known as the principal circulatory proteins in several organisms, forming about 50-60% of the entire number of plasma proteins [14]. Their conformational and physiological characteristics have been comprehensively explored [15; 16; 17]. Serum albumins in general are responsible for various conformational dynamics and binding aggregation in solution [18]. The albumin-drug interactions can appreciably control drugs' distribution volume and elimination rate. Hence, drug-albumin investigations may help to interpret a drug's metabolism, transportation mechanism, and its probable pharmacokinetic and pharmacodynamic profiles. A model protein that is frequently used to represent this albumins family in experimental studies is the bovine serum albumin (BSA) [19; 20]. BSA is a structural homologue to the human serum albumin (HSA) with a well-studied structure [21; 22; 23; 24; 25]. Numerous studies have been published reporting BSA-drug binding interactions using spectroscopic tools [18; 20; 26; 27]. Hence, in the current study, following the successful synthesis of the target non-symmetric bis-isatin derivative, and due to its potential anti-proliferative activity, its interaction with BSA was explored via spectroscopic and molecular docking approaches to gain insight into this compound's molecular features.  
Figure 1: Chemical structures of some anticancer agents bearing an isatin nucleus.  
Figure 2: Chemical structure of the title compound **3**.