Synthekine Reports Updated Clinical and Translational Findings for STK-012 in First-Line Non-Squamous NSCLC at AACR 2026
Synthekine, a clinical-stage biotechnology company focused on precision cytokine therapeutics, has released updated clinical and translational data for its investigational therapy STK-012. The results were presented during an oral session at the American Association for Cancer Research Annual Meeting 2026 in San Diego, highlighting the drug’s performance in combination with pembrolizumab and chemotherapy in patients with first-line, PD-L1-negative, non-squamous non-small cell lung cancer (NSCLC).
Promising Results in Difficult-to-Treat Patients
The updated findings underscore the potential of STK-012 to improve outcomes in patient populations that have historically responded poorly to standard chemoimmunotherapy. Among 36 efficacy-evaluable patients, the combination of STK-012 with pembrolizumab, pemetrexed, and carboplatin (PCT regimen) demonstrated a 50% objective response rate (ORR) in a cohort largely composed of PD-L1-negative individuals. This is notable because PD-L1-negative tumors are typically less responsive to immune checkpoint inhibitors, with conventional treatment approaches achieving ORRs in the range of approximately 23% to 32%.
Even more striking results were observed in patients harboring specific tumor suppressor gene alterations. In individuals with mutations in STK11, KEAP1, or SMARCA4—genetic profiles commonly associated with resistance to treatment—the combination therapy achieved a 61% ORR and a 100% disease control rate (DCR). These results significantly exceed historical benchmarks, where response rates in similar populations have been reported between 7% and 33%.
Encouraging Outcomes in High-Risk Genetic Subgroups
Particularly noteworthy were outcomes in patients with co-mutations in STK11 and KEAP1, a subgroup representing roughly 10% of first-line non-squamous NSCLC cases and known for especially poor prognosis. In this cohort, STK-012 plus PCT achieved a 50% ORR. Median progression-free survival (PFS) reached 5.5 months, while median overall survival (OS) had not yet been reached at a median follow-up of 6.8 months. The six-month OS rate stood at 88%, suggesting meaningful clinical benefit.
These results compare favorably to existing standards of care, where STK11/KEAP1 co-mutated patients typically experience ORRs of just 7% to 15%, median PFS of around three months, and median OS between 5.4 and 7.0 months. The improved outcomes observed with STK-012 suggest that the therapy may help overcome the intrinsic resistance mechanisms associated with these mutations.
Mechanism of Action: Precision Immune Activation
STK-012 represents a novel therapeutic approach as a first-in-class α/β IL-2 receptor-biased partial agonist. It is engineered to selectively activate antigen-experienced T cells—critical drivers of anti-tumor immunity—while minimizing activation of other immune cells such as natural killer (NK) cells, which are often linked to the toxicities seen with traditional IL-2 therapies.
This selective mechanism is designed to enhance immune responses specifically within the tumor microenvironment without triggering widespread immune activation, thereby improving both efficacy and tolerability. The drug’s design addresses a longstanding challenge in immuno-oncology: how to stimulate effective anti-tumor immunity without causing significant systemic side effects.
Safety and Tolerability Profile
Across 39 safety-evaluable patients, STK-012 combined with PCT demonstrated a favorable safety profile. There were no dose-limiting toxicities reported and no discontinuations attributed to STK-012. The most commonly observed treatment-related adverse events included rash or dermatitis (51%), nausea (51%), and fatigue (46%). Importantly, these side effects were generally manageable and reversible.
The absence of severe toxicity signals is particularly encouraging given the complexity of combining immunotherapy with chemotherapy, which can often amplify adverse effects. These findings suggest that STK-012 can be integrated into existing treatment regimens without significantly increasing the overall safety burden.
Translational Data Support Clinical Findings
In addition to clinical efficacy, Synthekine presented extensive translational data that provide biological insight into how STK-012 exerts its effects. These findings reinforce the observed clinical outcomes and demonstrate that the therapy is achieving its intended mechanism of action.
One key observation was the sustained exposure of STK-012, with a half-life of approximately 5.7 days. This extended half-life supports continuous pharmacodynamic activity throughout the standard three-week dosing cycle, ensuring consistent immune stimulation.
The therapy also induced targeted cytokine responses, including strong increases in interferon-gamma (IFN-γ) and IP-10, both of which are associated with effective anti-tumor immunity. Notably, there was minimal induction of inflammatory cytokines such as IL-6 and TNF-α, suggesting that STK-012 promotes a focused immune response rather than broad systemic inflammation.
Evidence of Robust T-Cell Activation
Further analyses revealed significant expansion of activated T-cell populations. In particular, there was a marked increase in 4-1BB+ CD8+ T cells, which play a critical role in tumor cell killing. At the same time, there was limited expansion of NK cells and regulatory T cells, indicating a highly selective immune activation profile.
Clonal expansion of T cells was also observed, with approximately 3.5% of circulating T cells derived from newly expanded clonotypes after just one treatment cycle. Importantly, greater clonal expansion correlated with improved clinical responses, suggesting a direct link between STK-012’s immune effects and patient outcomes.
Reversing Immune Resistance in Challenging Tumors
One of the most compelling aspects of the translational data was the evidence of immune reactivation in tumors with STK11 and KEAP1 co-mutations. These tumors are typically characterized by an “immune-cold” microenvironment, where T-cells are either absent or functionally suppressed.
STK-012 appeared to reverse this suppression by restoring proliferation of activated T-cells and reinvigorating exhausted T-cell populations, including PD-1+ CD8+ cells. Additionally, the therapy drove robust clonal expansion even in these highly suppressive tumor environments, indicating that it may be capable of overcoming one of the most significant barriers to effective immunotherapy.
Expert Perspectives
Synthekine’s leadership emphasized the significance of these findings for patients with limited treatment options. The company noted that while chemoimmunotherapy remains the standard first-line treatment for non-squamous NSCLC, many patients—particularly those with PD-L1-negative tumors or certain genetic alterations—derive only modest benefit.
The emerging data suggest that STK-012 could enhance the effectiveness of existing therapies by addressing the underlying immune resistance mechanisms. By selectively activating tumor-targeting T cells, the therapy may help convert immunologically cold tumors into “hot” ones that are more responsive to treatment.
The updated data from AACR 2026 build upon earlier findings presented at SITC 2025 and provide a more comprehensive view of STK-012’s clinical potential. With longer follow-up, deeper translational analyses, and encouraging signals in high-risk subgroups, the therapy is gaining attention as a promising addition to the NSCLC treatment landscape.
Further clinical development will be critical to confirm these results in larger patient populations and to better define the role of STK-012 in combination regimens. If future studies validate these findings, STK-012 could represent a meaningful advancement in the treatment of non-small cell lung cancer, particularly for patients who currently have limited effective options.
Overall, the data presented highlight a compelling combination of strong clinical activity, manageable safety, and clear biological rationale—positioning STK-012 as a potentially transformative therapy in the evolving field of cancer immunotherapy.
About the SYNERGY-101 Randomized Phase 2 Clinical Trial
Development of STK-012 is ongoing in SYNERGY-101, a global, randomized Phase 2 study evaluating STK-012 plus pembrolizumab and chemotherapy versus pembrolizumab and chemotherapy alone in first‑line, PD‑L1-negative non‑squamous NSCLC. The study is currently enrolling with the first patient dosed in November 2025. Synthekine has entered into a clinical trial collaboration and supply agreement with Merck, under which Merck provides Keytruda® (pembrolizumab) for use in the trial. Synthekine retains all commercial rights to STK-012.
Synthekine is harnessing the potential of cytokine therapeutics to develop selective immunotherapies designed to improve the treatment paradigm of cancer and inflammatory disease. Using insights on cytokine structure and function, the company engineers therapeutics designed to unlock the full efficacy potential of cytokines while avoiding their associated toxicities. Synthekine is applying principles of cytokine partial agonism and immunological specificity across multiple therapeutic areas to create a broad and deep pipeline of product candidates. These novel immunotherapies include modified cytokines and surrogate cytokine agonists
