Comparison of Delafloxacin (DLX) and Vancomycin (VAN) by Age and Gender in Two Phase 3 Trials in the Treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSIs)

Background: DLX is a novel investigational anionic fluoroquinolone being developed for oral or intravenous (IV) administration for infections caused by Gram‑positive organisms (including methicillin-resistant Staphylococcus aureus [MRSA]), Gram‑negative organisms, atypical organisms, and anaerobes.

Methods: Data on age and gender were reviewed from 2 randomized, double-blind trials of adults with ABSSSI. At baseline, patients had a lesion size ≥75 cm² with ≥ 2 signs of systemic infection. Patients received 5–14 days BID DLX 300 mg IV/ 450mg Oral, or VAN 15 mg/kg (based on the actual body weight) with aztreonam (AZ). Both studies included endpoints for objective response at 48-72 hrs based on ≥20% reduction of lesion size and investigator‑assessed response rates based on complete resolution of signs and symptoms (Cure) at Follow up (FU; Day 14) and Late Follow up (LFU; Day 21-28).

Results: In the combined patient pool, 1,510 patients (754 DLX, 756 VAN) in the Intent to Treat (ITT) had a mean age of 49.0 yrs for DLX and 48.1 yrs for VAN (1,314 were <65 yrs, 196 >65 yrs), and were majority male (62% DLX, 64% VAN). At baseline, digital mean lesion size was similar between both arms (321.1 cm² DLX, 344.7 cm² VAN).  Infection types included cellulitis (44.0%), wound infection (30.1%), major cutaneous abscess (25.1%) and burn infection (0.8%). Below is the comparison of DLX and VAN objective response at 48-72 hours in the ITT population:

Patient Population		DLX	VAN + AZ	Diff [95% CI]
Overall n/N (%)		613/754 (81.3)	610/756 (80.7)	0.8 (-3.2, 4.7)
Age n/N (%)	≤65	538/653 (82.4)	543/661 (82.1)	0.4 (-3.7, 4.5)
	>65	75/101 (74.3)	67/95 (70.5)	4.3 (-8.1, 16.6)
Gender n/N (%)	Male	381/468 (81.4)	397/485 (81.9)	-0.1 (-5.1, 4.8)
	Female	232/286 (81.1)	213/271 (78.6)	2.6 (-4.2, 9.3)

Investigator-assessed cure rates for all subjects at FU (55.2% DLX, 55.7% VAN) and LFU (69.0% DLX, 69.0% VAN) were similar. Overall, DLX had similar rates of related TEAEs between treatment groups regardless of age and gender. The most common AEs that were related to treatment were nausea (6.1% DLX, 4.3% VAN), pruritus (0.4% DLX, 2.3% VAN), and diarrhea (6.1% DLX, 2.0% VAN).

Conclusion: In a pooled analysis based on age and gender, DLX had comparable outcomes to VAN for the objective response at 48-72 hours. DLX was also well tolerated regardless of age or gender.