Bicycle Therapeutics disclosed in an abstract Sunday that 45% of bladder cancer patients responded to its experimental treatment in an early-stage study.

In 38 patients evaluated for efficacy, one saw signs of their cancer disappear completely, while 16 saw their tumors shrink by at least 30% — counting as a partial response in the Phase 1/2 study. The patients included in the analysis were treated with the dose of BT8009 that Bicycle is moving forward in registrational studies.

The median duration of response among 14 patients with confirmed responses was just over 11 months.

Bicycle is developing the antibody-drug conjugate-like therapy that it hopes will outclass Pfizer and Astellas’ urothelial carcinoma drug Padcev on safety, while matching its efficacy. In Padcev’s pivotal clinical trial in third-line advanced bladder cancer, the response rate was 44%, though in a group of 125 patients.

But Padcev can cause serious skin reactions and peripheral neuropathy — a type of nerve damage. In its trial, Bicycle noted 10 cases of treatment-related adverse events, but no grade 3 or higher cases of neuropathy, skin reactions or eye disorders among 45 patients evaluated for safety.

“The ADC field has been remarkable in what it’s achieved for patients, but we need to also realize that while these molecules have provided great advantages in terms of efficacy, there’s a lot to achieve in terms of tolerability profiles,” Bicycle CEO Kevin Lee told Endpoints News.

In a separate abstract, Bicycle detailed the peripheral neuropathy outcomes from its studies of BT8009 and another bicyclic drug, BT5528, across solid tumor types. Treatment-related peripheral neuropathy was reported in 42 of 149 patients who received BT8009, including just one grade 3 or higher case. No drug withdrawals were required for either treatment, according to the abstract.

Like Padcev, which is an antibody-drug conjugate, BT8009 targets nectin-4, a protein overexpressed in bladder and other cancers. Instead of an antibody to go after the protein, Bicycle’s therapy uses a synthetic bicyclic peptide, a type of two-ringed molecule the company hopes can bring the advantages of both antibodies and small molecules. The bicyclic peptide technology also inspired the company’s name.

Pfizer acquired Padcev via its $43 billion purchase of Seagen last year. Others, including Eli Lilly, are also developing next-generation nectin-4 targeted treatments.

Bicycle is expected to report results in about 20 patients on BT8009 in combination with Keytruda before the end of the year. And a Phase 2/3 study called Duravelo-2 looking at BT8009 as a monotherapy and in combination with Keytruda is currently enrolling advanced bladder cancer patients.

Editor’s note: This story was corrected to note Padcev is also an Astellas drug.