Oral lipid-based nanoformulation of tafenoquine enhanced bioavailability and blood stage antimalarial efficacy and led to a reduction in human red blood cell loss in mice

Figures & data

Table 1 Matrix of experiments for the preparation of microemulsions

Experiment number	Parameters
	Polyvinyl alcohol concentration	Na oleate concentration	Tween type	Tween volume	Essential oil volume	Temperature	Ethanol
1	1	1	1	1	1	1	1
2	1	1	1	2	2	2	2
3	1	2	2	1	1	2	2
4	1	2	2	2	2	1	1
5	2	1	2	1	2	1	2
6	2	1	2	2	1	2	1
7	2	2	1	1	2	2	1
8	2	2	1	2	1	1	2

Notes: PVA concentration =1% w/v (level 1) and 2% (level 2). Na oleate concentration =0.1% w/v (level 1) and 0.2% w/v (level 2). Tween surfactance type =20 (level 10) and 80 (level 2). Tween volume =140 μl (level 1) and 280 μl (level 2). Essential oil volume =0 μl (level 1) and 75 μl (level 2). Temperature =40°C (level 1) and 60°C (level 2). Ethanol =1 ml (level 1) and 2 ml (level 2).

Abbreviations: PVA, polyvinyl alcohol; v, volume; w, weight.

Table 2 Summary of the pharmacokinetic parameters for RTQ and MTQ (IV n=5, oral n=4)

Pharmacokinetic parameter	RTQ formulation				MTQ formulation
	IV administration (2 mg/kg)		Oral administration (20 mg/kg)		Oral administration (20 mg/kg)
	Average	SEM	Average	SEM	Average	SEM
Cmax (μM)	n/a	n/a	3.06	0.37	5.82	0.26
Tmax (h)	n/a	n/a	9.0	1.0	6.5	1.5
Apparent half-life (h)	43.7	1.5	38.3	4.1	44.7	1.3
Plasma CL (mL/min/kg)	1.84	0.07	n/a	n/a	n/a	n/a
Vd (L/kg)	2.34	0.00	n/a	n/a	n/a	n/a
Vss (L/kg)	6.81	0.00	n/a	n/a	n/a	n/a
AUC0–inf (min·μmol/L)	2,363	146	11,368	1,232	23,842	872
BA (%)	n/a	n/a	55	2	99	1.6

Abbreviations: AUC_0–inf, area under the curve 0 to infinity; BA, bioavailability; CL, clearance; C_max, peak concentration; h, hours; IV, intravenous; min, minutes; MTQ, microemulsion of tafenoquine; n/a, not applicable; RTQ, unformulated tafenoquine; SEM, standard error of the mean; T_max, time to peak concentration; Vd, volume of distribution; Vss, steady-state volume of distribution.

Table 3 Drug administration details per group

Group	Drug	Vehicle	Dose (mg/kg)	Frequency	Route	Treatment days
1 n=4	Vehicle control	HECT	N/A	QD	PO	3
2 n=4	PQ control	PBS	25	QD	PO	3
3 n=4	TQ	HECT	5	QD	PO	3
4 n=4	TQ	HECT	1	QD	PO	3
4 n=4	MTQ	Microemulsion	10	QD	PO	3
5 n=4	MTQ	Microemulsion	5	QD	PO	3
6 n=4	MTQ	Microemulsion	1	QD	PO	3

Note: PQ dose is expressed as the amount of base drug, not salt, given per kg of body weight.

Abbreviations: HECT, 0.5% hydroxyethyl cellulose (w/v) and 0.2% Tween 80 (v/v); MTQ, microemulsion formulation of TQ; N/A, not applicable; PBS, phosphate-buffered saline; PO, oral gavage; PQ, primaquine; QD, daily; TQ, tafenoquine; v, volume; w, weight.

Table 4 Characteristics of microemulsion formulations

Experiment number	Size (nm)	PDI	ZP (mV)	pH	Conductivity, σ (μS/cm)
1	267.0±26.0	0.71±0.22	−14.1±1.5	7.5±0.4	160.8±1.1
2	10.7±0.6	0.30±0.13	−14.2±0.6	6.8±0.6	132.8±2.1
3	355.5±25.3	0.59±0.11	−27.2±2.3	8.0±0.2	172.4±2.3
4	70.5±4.2	1.0±0.0	−53.3±0.8	7.6±0.5	231.0±1.0
5	214.5±11.3	0.34±0.02	−40.2±1.7	7.3±0.6	159.4±1.4
6	11.1±0.8	0.27±0.02	−19.2±1.5	7.3±0.3	201.3±1.2
7	153.9±9.3	0.56±0.12	−49.7±2.1	7.6±0.7	291.3±0.6
8	129.0±7.2	0.37±0.54	−12.9±1.3	7.6±0.2	223.3±2.9

Abbreviations: PDI, polydispersity index; ZP, zeta potential.

Figure 1 Percentage of TQ (of 5 mg/mL) dissolved in different components of microemulsion and the optimized microemulsion (n=3; mean ± standard deviation).

Abbreviations: PVA, polyvinyl alcohol; TQ, tafenoquine.

Figure 2 Mean whole blood concentration versus time graphs following oral administration of 20 mg/kg each of tafenoquine reference formulation and microformulation.

Note: Data shown represent mean ± standard error of the mean of n=4 mice.

Figure 3 Percentage loss of HuRBCs in SCID mice following oral administration of unformulated TQ and MTQ (n=4).

Abbreviations: HuRBC, human red blood cell; MTQ, microemulsion formulation of TQ; SCID, severe combined immunodeficiency; TQ, tafenoquine.

Figure 4 Peripheral blood levels of muRetics on day 7 (n=4).

Abbreviations: MTQ, microemulsion formulation of TQ; muRetics, mouse reticulocytes; TQ, tafenoquine.

Figure 5 Percentage HuRBC loss (n=4).

Notes: HuRBC % loss was calculated as ((day 0–day 7)/day 0) *100. Nano-tafenoquine = microemulsion formulation of tafenoquine; tafenoquine = unformulated tafenoquine.

Abbreviation: HuRBC, human red blood cell.