Doxycycline to Protect Heart Muscle After Heart Attacks

Background:

Matrix metalloproteinases (MMPs) are activated in myocardial ischemia, digesting key structural components in cardiac muscle in the setting of myocardial infarction and myocardial ischemia-reperfusion injury (Schulz, 2007, Annu. Rev. Pharmacol. Toxicol. 47, 211-42).

The antibiotic doxycycline is the only drug approved as an MMP inhibitor by Health Canada and the U.S. FDA for the treatment of periodontitis and rosacea at sub-antimicrobial doses.

Doxycycline decreases intracellular proteolysis, improves cardiac function, and reduces infarct size in animal models of ischemia-reperfusion injury (Cheung et al, 2002, Circulation 101:1833-39; Villarreal et al, 2003, Circulation 208:1487-92).

TIPTOP (Cerisano et al, 2014, Eur Heart J 35: 184-91) was a randomized open-label trial (110 patients) that studied the effect of 1-week doxycycline given post-percutaneous coronary intervention (PCI) in patients with anterior STEMI. Patients who received doxycycline showed improved echocardiographic indices at 6 months relative to untreated controls: left ventricular end diastolic volume index (LVEDVi) -8 mL ± 14 mL (P=0.004), left ventricular end systolic volume index (LVESVi) -6 mL ± 12 mL (P=0.02), and left ventricular ejection fraction (LVEF) +5% ± 12% (P=0.04). They also showed decreased infarct sizes (-6%, P=0.05) by single photon emission computed tomography (SPECT).

Rationale for study:

The TIPTOP pilot study showed promise for doxycycline therapy to decrease adverse ventricular remodeling post-PCI in STEMI patients. Animal models suggest that MMP activation occurs early in reperfusion (within 5 minutes) following severe ischemia, and the TIPTOP pilot showed that early treatment may result in measurable clinical benefit. However, the TIPTOP pilot was an open label study and used a low resolution approach to measure clinical outcomes.

This is a small-scale, single-centre Phase II trial with double blinding, and includes the use of magnetic resonance imaging to measure primary (LVESVi) and secondary outcomes (LVEF ad LVEDVi). The investigators anticipate beneficial effects of doxycycline, with patients showing lower levels of LVESVi and LVEDVi, increased LVEF by MRI, and reduced infarct sizes, compared to placebo at 3 months. The investigators also expect hospitalization and mortality rates due to cardiac events to be reduced in these patients.

If successful, the overarching goal is to develop a multi-center randomized, blinded, placebo-controlled trial to examine the effect of early doxycycline therapy in the setting of STEMI.

Inclusion criteria

• 18+ year old
• Diagnosis of acute ST-elevation myocardial infarction (STEMI)
• Primary STEMI
• Symptom onset of less than 12 hours
• Admitted to the Royal Alexandra Hospital in Edmonton, Alberta

Exclusion criteria

• Low risk inferior STEMI (total ST elevation plus depression <4mm)
• Cardiogenic shock
• Use of thrombolytics
• Prior history of myocardial infarction or heart failure
• Known hypersensitivity to tetracyclines
• Any concurrent medical condition expected to reduce life expectancy to <1 year
• Symptom onset to treatment (loading dose) time longer than 24 hours
• Poor renal function (eGFR<30 mL/min/1.73m2) or other contraindications to MRI (claustrophobia, pregnancy, PPM/ICD, sub-arachnoid clips, retained ocular foreign body)