The purpose of this study is to measure local and systemic safety and tolerability as well as improvement of Achilles tendon mechanical properties after a single peritendon injection of NGI226 MP in comparison to placebo MP in patients with mid-portion Achilles tendinopathy.

Inclusion Criteria:

• Written informed consent must be obtained prior to all study specific screening procedures, as close to the start of the screening period as possible.
• Presence of clinically (local Achilles tendon pain on tendon-loading activities, pain on palpation at the level 2-6 cm proximal to the calcaneal insertion) and ultrasound (local tendon thickening with hypoechogenicities and irregular fibre orientation) or MRI diagnosed mid-portion Achilles tendinopathy with symptoms present ≥8 weeks but <12 months at screening.
• The Achilles tendinopathy must have been refractory to at least 6 weeks of conservative treatment (physiotherapy, NSAIDS, RICE), but participants do not need to be in physiotherapy at the time of study entry.

Exclusion Criteria:

• Medical condition that would affect safety of peritendon injection (e.g., peripheral vascular disease, use of anticoagulant medication)
• History of recurrent, acute, symptomatic infections, including outbreaks of oral or genital herpes (> 2 symptomatic infections or >2 courses of anti-infective treatments required in the last 6 months; active systemic infection during last 2 weeks; known active infections (e.g. chronic or active Hepatis B or C, HIV) - simple cold excluded
• History or evidence of clinically significant cardiac or cardiovascular disease
• History of deep vein thrombosis, pulmonary embolism or evidence of primary or secondary hypercoagulable states
• History of surgical intervention for the treatment of tendinopathy, history of ankle surgery, ankle arthritis, traumatic, inflammation or deformity of ankle
• History of full-thickness tear or complete rupture of the Achilles tendon