Intratumoural treatment with tigilanol tiglate combined with systemic anti-programmed cell death receptor 1 (PD 1) immunotherapy may enhance anti-tumour immune responses and improve outcomes for patients with melanoma.~Primary Objectives:~1. To determine the maximum tolerated dose (MTD) or maximum feasible dose (MFD) level of a single intratumoural treatment of tigilanol tiglate (Tx1) administered in combination with pembrolizumab.~2. To assess the safety and tolerability of: i) A single treatment (Tx1) of intratumoural tigilanol tiglate at escalating dose levels (dose-escalation) administered in combination with intravenous (IV) pembrolizumab (200 mg); and ii) Repeat treatments of intratumoural tigilanol tiglate (maximum of 3 treatments) administered in combination with IV pembrolizumab (200 mg, Q3W). Repeat treatment(s) of intratumoural tigilanol tiglate to be administered at the same dose level at Tx1 as follows:~If the initially injected tumour(s) are not fully ablated, then intratumoural tigilanol tiglate Tx2 +/- Tx3 may be re-administered to the same tumour(s).~If the initially injected tumour(s) are fully ablated and additional pre-identified tumours can be treated, then intratumoural tigilanol tiglate, Tx2 +/- Tx3 may also be administered to those tumours.~Note: Tumours identified at Screening that are designated as not to be injected tumours (i.e. non-injected tumours for observation) cannot be treated at Tx1, Tx2 or Tx3.~Secondary Objectives:~To evaluate tumour response according to RECIST 1.1 criteria, including loco-regional control of injected tumour(s) and non-injected tumour(s), and survival in patients treated in this study.~To assess the safety and tolerability of ongoing treatment with pembrolizumab up to a total of 35 cycles (Q3W), including the combination with up to 3 treatments of intratumoural tigilanol tiglate (Q3W).~Exploratory Objectives:~1. To evaluate the tumour response of tumours following treatment with intratumoural injection with tigilanol tiglate in combination with pembrolizumab
A Phase Ib/IIa, multicentre, open label, dose-escalation study to evaluate the safety, tolerability, and preliminary effectiveness of intratumoural tigilanol tiglate in combination with intravenous pembrolizumab in adult patients with unresectable, Stage IIIB to IV M1c melanoma.