TABLE 21

CI values of two-drug combinations against HIV-1 III_a replication in MT4 cells CI < 1, = 1, and > 1 indicate synergism, additive effect, and antagonism, respectively, as described by Chou and Talalay (1984).

Drug Combinations^a	CI Values at:				Weighted Average CI Values^b	Assigned Symbol^c
Drug Combinations^a	EC₅₀	EC₇₅	EC₉₀	EC₉₅	Weighted Average CI Values^b	Assigned Symbol^c
AZT + DDC	1.469	1.321	1.189	1.107	1.211	– –
AZT + DDI	0.992	0.956	0.925	0.907	0.931	±
AZT + D4T	1.772	1.622	1.485	1.399	1.567	– – –
AZT + IFN	0.897	0.920	0.954	0.982	0.953	±
AZT + NEV	0.455	0.451	0.446	0.444	0.447	+ + +
AZT + ABT-538	0.580	0.603	0.628	0.647	0.626	+ + +
DDI + DDC	1.377	1.421	1.466	1.498	1.461	– – –
DDI + D4T	1.606	1.551	1.499	1.464	1.506	– – –
DDI + NEV	0.770	0.685	0.611	0.566	0.624	+ + +
DDI + IFN	0.619	0.711	0.819	0.905	0.812	+ +
DDI + ABT-538	0.619	0.602	0.594	0.593	0.598	+ + +
DDC + D4T	1.152	1.049	0.956	0.899	0.971	±
DDC + NEV	1.064	0.946	0.842	0.778	0.859	+
DDC + ABT-538	0.952	0.890	0.833	0.798	0.842	+ +
DDC + IFN	0.890	0.842	0.808	0.791	0.816	+ +
D4T + NEV	1.189	1.075	0.973	0.909	0.989	±
D4T + IFN	0.940	0.850	0.774	0.730	0.782	+ +
D4T + ABT-538	1.263	1.225	1.188	1.163	1.193	–
IFN + NEV	0.575	0.563	0.555	0.553	0.558	+ + +
IFN + ABT-538	0.921	0.778	0.673	0.617	0.696	+ + +
NEV + ABT-538	0.876	0.807	0.744	0.705	0.754	+ +

↵ a The combination ratios are designed to approximate the IC₅₀ ratios in which the seven drugs and their corresponding constituent components have the combination ratio of AZT/DDI/DDC/IFN/D4T/NEV/ABT-538 = 1:1600:50:16:10:40:4
↵ b Because the high degrees of effects are more important to the chemotherapy than the low degrees of effects, the weighted CI value was designed as CI_wt = [CI₅₀ + 2CI₇₅ + 3CI₉₀ + 4CI₉₅]/10
↵ c Degrees of synergism (+ signs) or antagonism (– signs) are based on the ranges of CI values as described in Table 4