A Single Direct Intratumoral Injection of TTI-621 (SIRPαFc) Induces Antitumor Activity in Patients with Relapsed/Refractory Mycosis Fungoides and Sézary Syndrome: Preliminary Findings Employing an Immune Checkpoint Inhibitor Blocking the CD47 Do Not Eat Signal
Bibliographic record
Abstract
Abstract Background CD47 is an immune checkpoint that binds to signal regulatory protein alpha (SIRPα) and delivers a “do not eat” signal to suppress macrophage phagocytosis. Tumor cells frequently overexpress CD47 to evade macrophage-mediated destruction. TTI-621 (SIRPαFc) is an immune checkpoint inhibitor consisting of the CD47 binding domain of human SIRPα linked to the Fc region of human IgG1 designed to both: 1) block the CD47 “do not eat” signal, and 2) engage macrophage Fcγ receptors with IgG1 Fc to enhance phagocytosis and antitumor activity. It is hypothesized that direct intratumoral injection of TTI-621 may enhance both local and systemic antitumor activity. Methods A Phase 1, multicenter, open-label study is ongoing to characterize the safety and tolerability of intratumoral injection of TTI-621 (NCT02890368). Eligible patients (pts) are adults with relapsed or refractory mycosis fungoides/Sezary syndrome or percutaneously-accessible solid tumors who have progressed on standard anticancer therapy or for whom no other approved therapy exists. Pts are enrolled in sequential cohorts to receive a single intratumoral injection of TTI-621 at increasing dose levels to characterize safety, pharmacokinetics, pharmacodynamics, and preliminary evidence of antitumor activity. Repeat TTI-621 intratumoral dosing has recently been initiated. Serial, post-injection biopsies are collected to assess the temporal impact of TTI-621 on the tumor microenvironment. Results Nine pts (6 M/3F, age 57-85 years) have been enrolled as of July 2017. Diagnoses include mycosis fungoides/Sezary syndrome (N=6), melanoma (N=1), leiomyosarcoma (N=1), and squamous cell carcinoma (N=1). A single intratumoral injection of 1 mg, 3 mg, or 10 mg TTI-621 has been well tolerated by all enrolled pts. The most frequently reported adverse events were fatigue in 5 pts, chills in 4 pts, and decreased appetite in 3 pts. All treatment-related AEs were Grade 1 or 2 in severity. No dose limiting toxicity has been observed to date. All 6 pts with mycosis fungoides/Sezary syndrome experienced decreases in tumor size and/or decreased circulating Sezary cells (3 of 3 pts) as determined by a decrease in a peripheral clonal T-cell populationor CD4:CD8 ratio after a single intratumoral injection of TTI-621. Responses ranged from loco-regional to systemic effects. One pt with localized refractory mycosis fungoides on the dorsum of the foot obtained a complete response of the injected lesion that is ongoing after 17+ weeks of follow up. NanoString analysis of peripheral blood and tumor tissue pre- and post-intratumoral injection of TTI-621 indicated alterations in genes associated with activation of the innate immune system and upregulation of IFN-associated genes. Conclusions These preliminary Phase 1 data suggest that mycosis fungoides and its leukemic variant, Sezary syndrome, are highly responsive to a single dose of TTI-621 delivered by intratumoral injection. One pt achieved a complete response of the injected lesion and 5 additional pts experienced decreases in tumor size and/or decreased circulating Sezary cells. Intratumoral injections were well tolerated by all pts. Evidence of innate immune activation was documented, consistent with the proposed function of TTI-621 as an innate immune checkpoint inhibitor. Disclosures Querfeld: Soligenix: Research Funding; Elorac: Research Funding; Celgene: Honoraria, Research Funding; MiRagen: Honoraria, Research Funding; Actelion: Honoraria, Research Funding; Medivir: Honoraria; Mallinckrodt: Honoraria; Mindera: Consultancy; Kyowa: Research Funding; Trillium Therapeutics: Research Funding; City of Hope: Employment. Thompson: Trillium Therapeutics: Research Funding. Taylor: Blue Print Medicines: Consultancy, Honoraria; Eisai Inc.: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Speakers Bureau; Trillium Therapeutics: Consultancy, Honoraria. Pillai: Trillium Therapeutics: Research Funding. Johnson: Trillium Therapeutics: Employment. Catalano: Trillium Therapeutics: Employment; Apotex Inc.: Employment. Petrova: Trillium Therapeutics: Employment, Equity Ownership. Uger: Trillium Therapeutics: Employment, Equity Ownership, Patents & Royalties. Irwin: Hoffmann La Roche: Employment, Equity Ownership; Trillium Therapeutics: Employment, Equity Ownership. Sievers: Trillium Therapeutics: Employment, Equity Ownership. Akilov: Seattle Genetics: Consultancy; Medivir: Consultancy; Actelion Pharmacuticals: Consultancy, Research Funding; Trillium Therapeutics: Research Funding.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".