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The first patient has received treatment with mavrostobart plus chemo in the phase 1/2 MORNINGSTAR trial for advanced solid tumors, including lung cancer.
The first patient has been dosed with mavrostobart (PT199) in combination with chemotherapy in the phase 1/2 MORNINGSTAR clinical trial for those with solid tumors, according to a news release from Phanes Therapeutics, Inc.
The study is set to evaluate patients with advanced or metastatic solid tumors, non-small cell lung cancer or pancreatic ductal adenocarcinoma.
Mavrostobart is an anti-CD73 antibody designed to overcome immune suppression in the tumor microenvironment by fully blocking both soluble and membrane-bound CD73. Unlike other CD73 inhibitors, it maintains its effectiveness at higher concentrations without a loss of activity, known as the “hook effect.” By addressing the limitations of existing treatments, mavrostobart may help boost the immune response against cancer and offer a new therapeutic option for patients.
CD73: protein that helps tumors evade the immune system; blocking it may boost immune response.
Tumor microenvironment: surrounding cells, molecules and blood vessels that interact with and support cancer cells.
ECOG performance status: scale used to measure how a disease affects a patient’s daily living abilities, with 0 being fully active and 1 meaning some activity restrictions.
In preclinical studies, mavrostobart demonstrated durable CD73 inhibition and enhanced T-cell activation, supporting its role in reversing tumor immune evasion, as per the MORNINGSTAR clinical trial page on the National Cancer Institute’s website. Its ability to sustain CD73 blockade without diminishing potency makes it a strong candidate for combination regimens, particularly in cancers where adenosine-driven immune suppression plays a major role. Ongoing investigations aim to evaluate its safety, efficacy and synergy with checkpoint inhibitors across multiple tumor types.
The MORNINGSTAR study is a first-in-human, multicenter trial which is currently evaluating the safety, tolerability, pharmacokinetics and preliminary efficacy of mavrostobart alone and in combination with a PD-1 Inhibitor or chemotherapy. In addition, China is also conducting a phase 1 clinical trial of mavrostobart with the clinicaltrial.gov ID, CTR20242381.
The trial is being conducted at two sites: University of Oklahoma Health Sciences Center in Oklahoma City, and MD Anderson Cancer Center in Houston, Texas.
Participants must have at least one measurable lesion and a confirmed diagnosis of advanced or metastatic solid tumors, non-small cell lung cancer or pancreatic ductal adenocarcinoma, depending on the trial part. Tumors must lack actionable genomic alterations such as EGFR or ALK mutations. Specific requirements vary by cohort, including prior treatment history and standard of care eligibility. Patients must have an ECOG performance status of 0 (fully active) or 1 (partially active), adequate organ function and be able to provide a tumor tissue sample for biomarker assessment unless medically inappropriate.
Patients are excluded if they are pregnant, breastfeeding or of child-bearing potential without effective contraception. Additional exclusions include active or recently treated autoimmune disease, recent or ongoing immunosuppressive therapy, severe immune-related side effects from prior treatments, untreated or progressing brain metastases, significant cardiac impairment, grade 3 (severe) or higher neuropathy, recent radiotherapy or current use of certain anticoagulants.
Advanced tumors often refer to cancer that is unlikely to be cured. Still, some advanced cancers can be managed for years with treatment and are considered chronic illnesses, according to the National Cancer Institute’s website. Treatment may aim to shrink tumors, slow growth, relieve symptoms, or extend life. "Advanced" can also describe cancer that has spread beyond its original site to nearby tissues, lymph nodes, or other parts of the body.
Additionally, metastases is the spread of cancer cells from where they first formed to another part of the body. Cancer cells travel through the blood or lymph system and form a new tumor, which is the same type of cancer as the original tumor. For example, breast cancer that spreads to the lungs is still considered breast cancer.
For more information regarding the MORNINGSTAR trial, please visit www.clinicaltrials.gov using the identifier: NCT05431270.
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