**2.7 Targeting CYPs**

The parent analogue, ANF (**94**), has long been recognized as displaying a broad range of pharmacological activities. Of particular note is its effects on CYP1. It has been shown that ANF (**94**) is capable of reversing CYP1B1-mediated drug resistance, increasing the efficacy of cytotoxic drugs. Simple ring opening of the flavone moiety releases a hydroxynaphthyl chalcone (**95**). Modification of the pendant phenyl ring was shown to impart modest CYP inhibition relative to ANF (**Table 3**). The parent phenyl (**96**) displays a CYP1B1 IC50 of 157.7 nM (c.f. ANF IC50 5.9 nM). Introduction of ring substituents enhances activity with the 4-F (**97**; 48 nM),


2-OCH3 (**98**; 37.7 nM), and 3-pyridyl (**99**; 16.7 nM), also with improved CYP1A2/B1 selectivity. Increasing the hydrophobicity of the phenyl moiety was detrimental to potency, but the introduction of a tetrasubstituted naphthyl moiety proved to be

*Cytotoxic activities of benzochalcones against MCF-7, MDA-MB-231, LCC6/P-GP, and MCF-7 cell lines.*

*Structural modification of ANF leading to a family of CYP1B1 inhibitors displaying high levels of cytotoxicity,*

**Compound MCF-7 MDA-MB-231 LCC6/P-gp MCF-7/1B1** ANF (**94**) 80.7 7.6 >100 82.3 8.5 >100 25.9 3.2 46.2 5.3 >100 32.3 4.5 48.1 3.7 79.6 4.9 48.6 2.9 >100 43.4 1.6 75.3 6.8 43.9 4.4 >100 7.6 0.7 19.8 2.8 8.0 2.3 12.7 1.7 6.3 1.4 15.8 2.2 9.6 1.3 15.1 1.8 46.8 4.7 48.9 4.1 >100 20.4 3.3

**IC50 values (μM)**

Of the modified ANF analogues reported, **100** and **101** displayed CYP1B1 inhibition level equivalent to ANF but with significantly enhanced selectivities of 150-

Examination of these analogues against MCF-7, MDA-MB-231, LCC6/P-gp, and MCF-7/1B1 revealed the 2-pyridyl chalcone analogue to be broad-spectrum active in both the wild type (MCF-7 and MDA-MB-231 cells) and also in the drug-resistant cells (LCC6/P-gp and MCF-7/1B1) (**Table 3**). Replacement of the phenyl moiety with a tetramethoxynaphthalene resulted in a drop in CYP1B1 activity (IC50 > 1000 nM), but the MCF-7 and LCC6/P-gp cytotoxicity increased. This presumably is a

The medicinal chemistry landscape is a mobile one. Approaches that were viewed as unviable mere 5- to 10-years ago are now gaining traction. The introduction of PAINS filters has stymied some areas of medicinal chemistry development,

reexamination of the type of screening filters applied. This is especially relevant to the potential development of chalcones in the anticancer drug space. It has been

correctly; but in other areas, the changing paradigms may necessitate a

highly efficacious [99] (**Figure 24**).

**3. Conclusions**

**91**

**Figure 24.**

**Table 4.**

*see* **Table 3** *for details of "R" [99].*

*Chalcones: Potential Anticancer Agents DOI: http://dx.doi.org/10.5772/intechopen.91441*

and >200-fold (ANF, CYP1A2/B1 = 3.1) (**Table 3**).

consequence of increased cellular uptake [99] (**Table 4**).

#### **Table 3.**

*Inhibitor potency of modified chalcones against CYP1 enzymes.*

*Chalcones: Potential Anticancer Agents DOI: http://dx.doi.org/10.5772/intechopen.91441*

**Figure 24.**

selective inhibition of TrxR, and induction of cell apoptosis. Mechanistically, the U498C mutation of TrxR was performed to support the covalent mechanism. As a result, this compound could significantly decrease the cellular thiol level and induce

The parent analogue, ANF (**94**), has long been recognized as displaying a broad range of pharmacological activities. Of particular note is its effects on CYP1. It has been shown that ANF (**94**) is capable of reversing CYP1B1-mediated drug resistance, increasing the efficacy of cytotoxic drugs. Simple ring opening of the flavone moiety releases a hydroxynaphthyl chalcone (**95**). Modification of the pendant phenyl ring was shown to impart modest CYP inhibition relative to ANF (**Table 3**). The parent phenyl (**96**) displays a CYP1B1 IC50 of 157.7 nM (c.f. ANF IC50 5.9 nM). Introduction of ring substituents enhances activity with the 4-F (**97**; 48 nM),

**Ar CYP IC50 values (nM) IC50 ratio**

ANF **94** 5.9 1.3 80.3 3.6 18.0 3.6 13.6 3.1 Ph **95** 157.7 18.5 >1000 >1000 >6.3 >6.3 4-FPh **96** 48.3 8.2 >1000 >1000 >20.7 >20.7 2-OCH3Ph **97** 37.8 5.8 556.6 28.7 >1000 14.7 >26.5 3-Pyridyl **98** 16.7 3.7 117.1 18.9 227.0 25.2 7.0 13.6

**99** 4.9 0.6 161.3 17.4 734.7 31.2 32.9 149.9

**100** 4.8 0.5 51.8 9.7 >1000 10.8 >208.3

*Inhibitor potency of modified chalcones against CYP1 enzymes.*

**1B1 1A1 1A2 1A1/1B1 1A2/1B1**

the expression of reactive oxygen species (ROS) [98].

**2.7 Targeting CYPs**

*Translational Research in Cancer*

**Table 3.**

**90**

*Structural modification of ANF leading to a family of CYP1B1 inhibitors displaying high levels of cytotoxicity, see* **Table 3** *for details of "R" [99].*


**Table 4.**

*Cytotoxic activities of benzochalcones against MCF-7, MDA-MB-231, LCC6/P-GP, and MCF-7 cell lines.*

2-OCH3 (**98**; 37.7 nM), and 3-pyridyl (**99**; 16.7 nM), also with improved CYP1A2/B1 selectivity. Increasing the hydrophobicity of the phenyl moiety was detrimental to potency, but the introduction of a tetrasubstituted naphthyl moiety proved to be highly efficacious [99] (**Figure 24**).

Of the modified ANF analogues reported, **100** and **101** displayed CYP1B1 inhibition level equivalent to ANF but with significantly enhanced selectivities of 150 and >200-fold (ANF, CYP1A2/B1 = 3.1) (**Table 3**).

Examination of these analogues against MCF-7, MDA-MB-231, LCC6/P-gp, and MCF-7/1B1 revealed the 2-pyridyl chalcone analogue to be broad-spectrum active in both the wild type (MCF-7 and MDA-MB-231 cells) and also in the drug-resistant cells (LCC6/P-gp and MCF-7/1B1) (**Table 3**). Replacement of the phenyl moiety with a tetramethoxynaphthalene resulted in a drop in CYP1B1 activity (IC50 > 1000 nM), but the MCF-7 and LCC6/P-gp cytotoxicity increased. This presumably is a consequence of increased cellular uptake [99] (**Table 4**).

#### **3. Conclusions**

The medicinal chemistry landscape is a mobile one. Approaches that were viewed as unviable mere 5- to 10-years ago are now gaining traction. The introduction of PAINS filters has stymied some areas of medicinal chemistry development, correctly; but in other areas, the changing paradigms may necessitate a reexamination of the type of screening filters applied. This is especially relevant to the potential development of chalcones in the anticancer drug space. It has been

consistently shown that not only do these agents possess high levels of antiproliferative activity as single agents, they synergise well across a significant number of clinically used anticancer drugs.

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As this field progresses, careful reevaluation of off-target effects, compound specificity, and promiscuity will remain key, but there is significant potential for transformation of chalcones into true clinical compounds. It is worth noting that it is the role of the medicinal chemist to modulate the unfavorable effects of lead compounds in the development of clinical candidates. This, perhaps though is best left in an academic environment until "compound cleaning" to a true development candidate can be achieved.
